GM mistakes don’t happen because you’re a bad Game Master. They happen because you’re a busy human with a job, a life, and a group of friends who also have lives and jobs.
It’s 7:30 PM. Your players arrive at 8. Work ran long, you wolfed down dinner at your desk, and your “prep” is a half-read module tab and three cryptic bullet points on your phone. You want to give your group a great session… but instead you feel rushed, scattered, and quietly guilty that you’re not “doing it right.”
Here’s the good news: most rough sessions don’t come from obscure rules you don’t know or the fact you didn’t write a novel-length backstory. They come from a small handful of repeatable habits and patterns in how you prep, run, and respond at the table. Change those patterns, and your games improve fast.
By the end of this post, you’ll know the five most common GM mistakes that happen over and over, plus a simple “do this instead” fix for each that you can try in your very next game. We’ll also talk about how to lean on tools like one-page dungeons and plug-and-play resources when your prep time evaporates.
Here’s the thing: you don’t have to fix everything at once. Even applying one quick fix this week will make your table feel more confident, more responsive, and a lot less stressful to run.
Why GM Mistakes Happen (And Why That’s Okay)
Before we dig into specific mistakes, it’s worth saying this out loud: every GM you admire has made these mistakes. Some of them are still making them, just less often, and with better recovery.
Most GMs learn by doing. Maybe you:
- Picked up a big hardcover, grabbed a few friends, and volunteered because no one else would.
- Watched actual-play streams where the GM has infinite prep time and a full production team.
- Ran a published adventure and tried to “do it justice” by following it scene by scene.
None of that is wrong. But it does quietly train you to focus on the wrong parts of the job:
- You over-prepare lore and under-prepare situations.
- You memorize boxed text instead of thinking about how the scene can change.
- You assume “good GMing” means encyclopedic rules knowledge instead of simple, reliable processes.
So when players zig instead of zag, or when you’re tired and under-prepped, those habits show up as:
- Railroading to protect your notes.
- Long pauses while you scramble for ideas.
- Sessions that meander because you don’t have a clear sense of how to go from hook to escalation to fallout.
The important part: none of this is a moral failing. You don’t need to become a different personality type or read every rulebook cover to cover. Small changes to how you prep and what you pay attention to will get you much further than chasing some mythical “perfect GM” standard.
If you enjoy going deep, there are fantastic deep-dive resources on GM craft—books like The Game Master: A Guide to the Art and Theory of Roleplaying, Never Unprepared: The Complete Game Master’s Guide to Session Prep, or Return of the Lazy Dungeon Master on DriveThruRPG are all excellent long-form reads. But you don’t have to finish any of those before your next game.
This post will focus on practical things that are genre and system-neutral. No matter what system you are running, the same core patterns apply:
- Focus your prep on situations over scripts.
- Use tools (like 1d100 tables and one-page dungeons) instead of raw brainpower when you’re tired.
- Make small, deliberate tweaks to your pacing, spotlight, and stakes.
You’re already doing the hardest part: sitting down behind the screen. The rest is just technique.
GM Mistake #1: Prepping the Wrong Stuff
Most GMs don’t suffer from too little prep. They suffer from prep in the wrong places.
You sit down with good intentions and end up:
- Writing pages of backstory about an ancient empire no one will ever ask about.
- Plotting a scene-by-scene narrative like a movie script, only for the players to kick in a side door you never planned for.
- Spending three hours on lore and exactly ten minutes on “what actually happens at the table tonight.”
On paper, you’re “well prepared.” In practice, you hit game night and still feel oddly unready. The session starts, someone says “So where are we again?” and you realize you don’t have a clear opening scene, goal, or conflict in your pile of notes.
That’s where the pain creeps in:
- Burnout: Prep starts to feel like homework instead of play.
- Wasted effort: Whole chunks of your beautiful notes get skipped because the players choose a different path.
- Lingering anxiety: Even after all that work, the session’s structure still feels fuzzy.
If you’ve ever stared at your five pages of notes and thought “Why do I still feel unprepared?”, this is why.
Why It Quietly Wrecks Sessions
When most of your prep is backstory and scripted scenes, you’re setting a trap for yourself.
At the table, you tend to:
- Railroad to protect your investment. You nudge or shove players back toward the content you planned so the prep doesn’t “go to waste.”
- Or you blank completely when they go sideways, because all your notes assume a specific path that now no longer exists.
From the players’ side, those sessions often feel:
- Slow to start with lots of exposition, not much to do yet.
- Aimless or overstuffed, where either nothing seems important, or everything is equally loud and detailed.
- Handwavey the moment they leave the prepared path, the world suddenly gets vague and sketchy.
The irony: the more you prep the wrong things, the harder it gets to run loose, confident, responsive games.
The Fast Fix: Prep Situations, Not Scripts
Instead of prepping a story that must happen, prep a situation that could go a lot of ways.
A simple framework you can reuse for almost any session looks like this:
- Location(s): Where is tonight’s action taking place? A dungeon, a derelict, a city block, a space station?
- Problem(s) or Tension: What is going wrong, about to go wrong, or could go wrong if the players do nothing?
- Moving Pieces (NPCs & Factions): Who cares about this situation, and what are they likely to do next?
Good news: a lot of the hard work is already done for you if you use one-page dungeons. Fantasy adventures like Hall of Mirrors and Vault of the Runemark are basically pre-built situations: a focused map, a strong core problem, and just enough detail to spark your own ideas. On the sci-fi side, one-page adventures like Cryo-Strain and Meltdown Protocol do the same thing for derelicts and disaster scenarios.
Try This Before Your Next Session
You don’t need a big reset to feel the difference. For your very next game, try this tiny experiment:
- Pick one short adventure you find interesting.
- Highlight 3 cool locations, 2 NPCs or monsters (with motives about what they want), and 1 ticking clock that represents an approaching threat.
- Ignore the rest of the text unless it comes up at the table.
You’ll walk into the session with a clear situation instead of a fragile script, and you’ll feel a lot less pressure to “use everything you prepped,” because what you prepped is flexible by design.
GM Mistake #2: Freezing When Players Go Off the Rails
You’ve prepped the “main” adventure hook. You know who hired the party, what the mission is, where the dungeon or derelict is located.
Then the players:
- Decide to follow the throwaway bartender you named off the top of your head.
- Ignore the quest-giver completely and go investigate a random alley, docking bay, or side door.
- Ask for extremely specific details you did not prep: “What’s in this cargo container?”, “What’s the name of this bar and what’s on the menu?”, “What weird thing is happening over there right now?”
And your brain just… stalls. The GM response is almost always the same:
- Panic: you feel put on the spot and worry whatever you say will be “wrong.”
- Stalling: you flip through notes, mumble, or try to redirect them back to your prepared content.
- A hard “no” to protect your prep: “There’s nothing interesting there,” “That NPC just leaves,” “Customs waves you through, don’t worry about it.”
In the moment, this feels safe. You’re trying not to wreck your plans. But over time, it teaches your table something you probably don’t intend.
Why It Quietly Wrecks Sessions
Players are always testing the edges of the fiction. Not in a malicious way but just by being curious, weird human beings.
When the only interesting things in your world are the bits you prepped in advance, your players eventually learn:
- The world only really exists where the GM has notes.
- Their choices don’t matter as much as “guessing what the GM wants us to do.”
On your side of the screen, this leads to a nasty feedback loop:
- You feel anxious and avoidant about improv, because every time they go off-script you’re back in that panicked space.
- You start over-prepping in fear of “what if they go sideways again?”, which burns even more time and still doesn’t cover every possibility.
The result is a game that looks open on the surface but feels narrow in play. Players sense the invisible rails, and you feel like you’re wrestling your own prep instead of collaborating on a story.
The Fast Fix: Use Random Tables as Your Improv Engine
The good news is that you don’t need to invent everything from scratch under pressure. You just need structured surprise.
Instead of trying to hold a whole universe in your head, put 2 or 3 random tables within arm’s reach and let them do the heavy lifting whenever players poke at the unknown.
For example:
- Use something like 1d100 Interstellar Encounters to decide what’s happening in that unplanned corridor, docking bay, or back alley.
- Use 1d100 Sci-Fi NPCs when a throwaway contact suddenly becomes important and you need a goal, quirk, or secret right now.
- Use 1d100 Pocket Loot in fantasy games to answer “What’s in their pockets?” with something more interesting than 3d6 gold pieces.
- Use 1d100 Cursed Locations or 1d100 Sci-Fi Junk when players decide to explore some weird place or rummage through cargo they were never meant to open.
Random tables are permission slips to improvise. When you roll on them, you’re telling yourself: “Whatever comes up, I will treat as true and find a way to make it matter.”
With just a couple of those within reach, going off the rails stops being a threat and starts being an opportunity.
Try This Before Your Next Session
Here’s a simple way to test this out in your very next game:
- Pick 2 or 3 random tables that match your game’s vibe.
- When players go off script, do three things:
- Roll once on the most relevant table.
- Commit to making that result true in the fiction.
- Ask yourself: “How could this connect to what’s already happening?”
Random tables gave you raw material, and a single question: “How does this tie into the current fiction?”
If you like this style of play, you can go even further and build whole adventures out of a handful of rolls. We’ll dig into that in more detail in a dedicated post on turning random tables into fully fleshed-out adventures, but for now, just putting a couple of good tables next to your GM screen will make going off the rails feel a lot less scary.
GM Mistake #3: Flat Pacing (No Peaks, No Breath)
Some sessions never quite lift off. Others feel like a non-stop action reel with no chance to breathe. Or you get a night that’s just… a sequence of scenes that don’t really build on each other.
Flat pacing usually looks like:
- Games that start slow and never really ramp up into a meaningful problem or climax.
- Nights of constant combat with no downtime, reflection, or character moments.
- Sessions that feel like disconnected scenes without escalation where things happen, but nothing really builds.
On paper, a lot happened. At the table, it all blurs together.
Why It Quietly Wrecks Sessions
Good pacing isn’t about constant high energy, it’s about contrast.
When the pacing is flat:
- Players
- Lose track of what’s actually important versus what’s filler.
- Stop feeling tension or relief because everything is the same emotional volume.
- Remember the general “vibe” of the campaign, but not specific moments or turning points.
- You, the GM
- Feel like sessions blur together into one long, indistinct adventure.
- Catch yourself thinking, “We’re just slogging through,” even when a lot of stuff happened.
And because nothing stands out, it’s hard to tell which parts of your prep are pulling their weight and which parts you can safely drop.
The Fast Fix: Use a Simple 3-Beat Session Structure
You don’t need an intricate act diagram to fix this. A simple three-beat structure will do more for your pacing than any number of flowcharts.
For most sessions, aim for:
- Beat 1: Hook & Arrival
- How do the characters enter the situation?
- What immediately grabs their attention, threatens them, or tempts them?
- Beat 2: Escalation & Complication
- What makes things worse or weirder once they’re engaged?
- What unexpected element shows up and forces them to rethink their approach?
- Beat 3: Fallout & New Question
- What are the consequences of their choices this session?
- What new question, threat, or opportunity do they walk away with?
To keep this from feeling formulaic, insert one deliberate complication in the middle of the session using a random table. That gives you a guaranteed “spike” of tension and surprise without needing to pre-script everything.
Try This Before Your Next Session
For your next game, don’t try to overhaul everything. Just do this:
- Write one sentence for each beat.
- Hook & Arrival: “The crew docks at an aging refuelling station on the edge of a nebula, answering a vague distress call.”
- Escalation & Complication: “Midway through negotiations, an impossible sensor reading suggests the station itself is drifting into a space-time anomaly.”
- Fallout & New Question: “If they survive, they learn the anomaly was triggered by someone on purpose.”
- Pick one complication table or page from a 1d100 PDF.
- In sci-fi, that might be 1d100 Space Anomalies or 1d100 Interstellar Encounters.
- In fantasy, it might be Tavern Tales: 100 Adventurous Rumours or a favourite encounter table.
- Decide in advance: “At roughly the halfway mark, I will roll and let this twist the situation.”
- No matter what the result is, you commit to weaving it into the current scene as a real, consequential development.
That one simple habit (three beats plus a mid-session complication roll) will give your sessions a natural rise, spike, and landing. Later, when we talk about low-prep session structures in more detail, you can layer on more nuance. For now, this is enough to make your pacing feel intentional instead of accidental.
GM Mistake #4: Unbalanced Spotlight (Some Players Vanish)
Every group has that one player who can talk their way through anything, or the tactics gremlin who always has a plan. Which is fine, until it isn’t.
Over time, you can end up with:
- One or two players who dominate social scenes or tactics, always jumping in first when it’s time to make a choice, talk to an NPC, or roll the crucial skill.
- Quieter players who rarely get scenes tailored to them, so they hang back, roll the occasional attack or saving throw, and gradually fade into the background.
No one set out to make it “The Main Character Show,” but that’s how it starts to feel.
Why It Quietly Wrecks Sessions
When spotlight drift goes unchecked, it doesn’t usually explode in one dramatic argument. It erodes things slowly.
It leads to:
- Bored, checked-out players scrolling their phones or waiting for “their turn” that never really comes.
- Out-of-game resentment, especially if someone feels like their character concept never mattered.
- A quiet sense that the campaign is really “for” certain characters only, and everyone else is along for the ride.
As GM, you might notice:
- Sessions start to blur together because the same few voices are driving every major scene.
- You catch yourself thinking, “We’re just slogging through,” when what’s really happening is that half the table isn’t engaged.
The good news is that you don’t have to clamp down on the talkative players. You just need a simple way to track who’s getting attention and a habit of pointing scenes at the people who need it most.
The Fast Fix: Rotate Scenes and Seed Hooks From NPCs
Your first tool is a spotlight tracker. Nothing fancy, just a list of PC names in your notes. Every time a scene focuses on a character, you put a tick mark next to their name. After a while, a pattern emerges:
- Some players are at four or five ticks.
- Others are sitting at one… or none.
That visual reminder nudges you to aim the next scene, question, or problem at someone who hasn’t had much time in the light yet.
Your second tool is deliberate scene starts. Once or twice a session, intentionally start a scene where a quieter character is the obvious first responder. For example:
- The debt collector who shows up is connected to the PC in question.
- The ominous artifact resonates with energy linked the PCs backstory.
- The nervous informant specifically asked to meet the PC, not the group.
The easiest way to do this without rewriting your entire campaign is to use NPCs as spotlight delivery systems where people who show up with baggage, debts, or history that aim directly at a specific PC.
Tables like 1d100 Doomed Wanderers are perfect for this in fantasy and dark settings. Each entry is a tragic, half-broken NPC who can be tied to a character’s past, ideals, or family with a single sentence. In sci-fi campaigns, 1d100 Sci-Fi NPCs gives you goals, quirks, and secrets you can assign directly to “that quiet player’s old war buddy” or “the fixer who only trusts the medic.”
When those NPCs walk on stage, they don’t address “the party.” They address that specific character, forcing the rest of the group to pivot their attention there too.
Try This Before Your Next Session
For your next game, try this simple routine:
- Write one custom question or offer for each PC.
- For example: “The ranger gets a rumour about poachers in her old forest,” “The engineer’s old crewmate shows up with a dangerous job,” “The warlock’s patron sends a messenger demanding a favour.”
- These don’t all have to fire in one session but having them ready makes it easy to aim scenes.
- Plan one scene where only that PC is the obvious first responder.
- Maybe the noble’s family name is on the cursed will.
- Maybe the hacker’s credentials are needed to access the station’s black-market network.
- Design it so that it would be genuinely weird for anyone else to step in first.
- Track spotlight with tick marks and adjust on the fly.
- As you run the session, add a tick every time a PC is at the centre of things.
- If someone is falling behind, consciously nudge the next hook or consequence toward them.
You don’t need to wrestle control away from your enthusiastic players. You just need a lightweight system that reminds you to rotate the camera and a few NPCs who care deeply about the characters who usually hang back. Over a few sessions, the table will start to feel much more like an ensemble cast and a lot less like “that one person’s show.”
GM Mistake #5: Stakes Without Teeth (or Consequences Without Clarity)
Stakes problems usually show up in one of two ways:
- Outcomes don’t really matter. Whether the party wins, loses, or walks away, the story basically continues as if nothing happened.
- Consequences are arbitrary and invisible. Disasters drop out of nowhere (rocks fall, everyone dies) or punishments feel disconnected from player choices.
In both cases, players:
- Don’t really know what they’re risking when they step into danger.
- Don’t feel a meaningful payoff when they succeed. It’s just another pile of generic loot or a vague “you did it.”
Without clear stakes, even well-run sessions can feel strangely hollow.
Why It Quietly Wrecks Sessions
RPGs thrive on meaningful decisions. If players can’t see what’s on the line, or if what happens next doesn’t seem tied to their choices, tension evaporates.
- It reduces tension when everything is “fine anyway.”
- If the town is always saved, the cargo is always delivered, and the villain always escapes but in a way that doesn’t really affect anything, players start disengaging. Their choices feel decorative, not decisive.
- It breeds distrust when consequences feel random or unfair.
- If terrifying fallout drops with no warning, or the GM seems to be punishing them for guessing “wrong,” players turtle up. They stick to safe, boring options because any step off the path might trigger a disproportionate hammer.
Over time, you get a table that either doesn’t care what happens or is too cautious to do anything interesting, neither of which is fun.
The Fast Fix: Make 2 or 3 Concrete Stakes Obvious Up Front
You don’t need a flowchart of every possible outcome. You just need 2 or 3 clear, concrete stakes in play before things heat up.
Use this simple pattern when you frame a mission, dungeon, or situation:
- What might they gain?
- Money, reputation, allies, powerful tools, leverage.
- What might they lose?
- Lives, limbs, sanity, relationships, safe places, precious items.
- Who or what changes if they walk away?
- Which NPC suffers? Which faction advances? What horror is unleashed or left to fester?
You don’t have to info-dump all of this out of character. You can show it through rumours, ominous hints, and NPC warnings. The key is that, from the players’ perspective, they can tell that “If we succeed, X happens,” and “If we fail or bail, Y happens.”
Long-term, items, curses, and cults are fantastic vehicles for stakes:
- Cursed treasure that slowly warps people and places is baked into 1d100 Dark Treasures. A single strange relic can become an ongoing problem, temptation, or source of power that colours multiple sessions.
- Escalating villain organizations from 1d100 Cults give you a clear “if you ignore them, they advance their plans” engine. Their rituals, recruitment, and influence become visible markers of failure or of hard-won victories when the party pushes back.
- Adventures like Horror in Elwyn, Horror in Weizenville, and even a tighter dungeon like Hall of Mirrors work well because the stakes are thematic and visible: drowning grief, moral rot, or reality-bending mirrors that change people in lasting ways.
When players can see the shape of the danger and the shape of the reward, their choices suddenly snap into focus.
Try This Before Your Next Session
For your next game, don’t worry about building an intricate consequence tree. Just answer two questions about whatever situation you’re running:
- “If the party fails tonight, what definitely changes in the world?”
- Maybe a cult completes a minor ritual and the next town over starts seeing omens.
- Maybe a rival crew gets the salvage contract and gains a new ship.
- Maybe the cursed treasure they left behind finds its way into the hands of someone they care about.
- “If they succeed, what visible reward and new problem appear?”
- Reward: They get paid, gain influence, or claim a powerful (and possibly dangerous) item.
- New problem: Someone notices, someone resents it, or the thing they claimed starts to have side effects.
Write each answer as a single sentence in your notes and make sure you either say it out loud through NPCs or show it clearly in the fiction. Do that, and your game stops feeling like a series of disconnected fights and starts feeling like a story where what the players do actually matters.
Putting It All Together in A One-Week GM Tune-Up Plan
You don’t have to fix your entire GM style overnight. Treat this post like a one-week tune-up you can actually finish.
First, here’s a quick checklist of the five common GM mistakes we’ve talked about:
- Prepping the wrong stuff: Lots of lore, not enough situation.
- Freezing when players go off the rails: Panic when they ignore your “main” hook.
- Flat pacing (no peaks, no breath): Sessions that never really rise or fall.
- Unbalanced spotlight (some players vanish): One or two “main characters,” everyone else fades.
- Stakes without teeth (or consequences without clarity): Outcomes don’t matter, or feel arbitrary.
This week, try the following:
- Pick one or two mistakes that hit you hardest. Maybe you over-prep lore. Maybe you dread improv. Maybe you know one player is stealing a lot of spotlight.
- Apply the “Try This Before Your Next Session” steps for those mistakes.
- For prep, build a situation instead of a script.
- For improv, keep 2 or 3 random tables beside you.
- For pacing, sketch a three-beat structure.
- For spotlight, use a simple tick-mark tracker.
- For stakes, write one clear “if we fail” and one clear “if we succeed.”
- After the game, take two minutes to jot down:
- What felt easier for you behind the screen?
- What did your players react to, lean into, or talk about afterward?
That tiny reflection loop is where you really start to level up. You’re not trying to become The Perfect GM, instead you’re just nudging your process one step closer to the table you actually want to run.
From here, good next steps include:
- A deeper dive on fast prep and one-page dungeons (for when you’re low on time).
- A focused article on how to write RPG villains players never forget.
- A craft-focused guide to horror in fantasy RPGs.
- A dedicated breakdown of turning random tables into fully fleshed-out adventures rather than disconnected scenes.
Those pieces build on what you’ve started here and give you more detailed tools in each area.
Get a Free 1d100 Loot Table for Your Next Session
If you’re short on prep and want something you can literally drop into this week’s game, we’ve got a free tool for you.
When players go off the rails, search bodies, loot a desk, or poke around in places you didn’t plan, it’s easy to fall back on “uh… you find some coins, I guess.” That’s fine once in a while, but it’s a missed opportunity for story.
You can fix that with one simple resource: a plug-and-play loot table that always has something interesting ready. You can grab a free, table-ready version of 1d100 Pocket Loot as a PDF here.
Join the Terry Herc Games newsletter to download it, and you’ll also be the first to hear about new products, special offers, and things you can actually use at the table.
If you want your next session to feel a little sharper, a little weirder, and a lot easier to prep, start by giving yourself better tools to improvise with. The free 1d100 Pocket Loot PDF is a good first step.
