Game Mastering

I am a fairly inexperienced GM. I’ve been running games since September 2018, in three systems, and for two of those I relied heavily on pre-written modules.

I can get pretty lost when I have to improvise. I can get stuck with analysis paralysis if it’s clear that a rule applies, but it’s not clear which or how, and so I need to make a ruling. I’ve been guilty of the classic mistakes, like just shutting down player actions I wasn’t prepared to handle, and heavily railroading people through my plot.

But I try to improve. I read a lot of GMing resources, I reflect on my sessions, and I ask for advice.

This memo is a collection of my advice, to you.

Action adjudication

Only roll when the outcome is in doubt

PCs are, generally, competent. So when a PC needs to do something, there are four cases:

  1. If the action is easy, the PC just does it. Don’t roll for easy things.

  2. If the action is challenging, but there are no external factors which put the outcome in doubt (like a hard time limit, or a threat of discovery), the PC just does it. You might want to roll to find out how well they do it (maybe it takes hours longer than hoped), but fundamentally they do it.

  3. If the action is challenging, and there are external factors which put the outcome in doubt, roll for it.

  4. If the action is impossible, the PC just doesn’t do it. Don’t roll for impossible things.

Failure doesn’t just mean “you fail”

We’ve got a case (3): the thing is challenging, and the outcome is in doubt. The player rolls… and they miss their target.

If possible, don’t just stop the action. Sometimes that is appropriate, but often it can be more interesting for the PC to succeed, but in such an awful way that they wish they hadn’t. Or maybe they fail, but still learn how they could succeed in the future.

For example, let’s say the PC is picking the lock on a safe and they miss their roll. Which one of these three outcomes do you not want to narrate:

  1. “You pick the lock, but as you reach for the money inside your hand trips a laser sensor, setting off the alarm! You hear the footsteps of the guards outside, they’ll be here in seconds.”

  2. “You carefully examine the lock, and quietly swear under your breath: you’ll need some explosives or special-purpose picks before you can crack this safe open.”

  3. “You fail to open the safe.”

Here, (1) has the player succeed, but with a significant complication; (2) has the player fail, but gives them a path forwards; and (3) does neither.

In combat, the PCs never just miss

In a fight, an experienced swordsman doesn’t just flail around with their sword and hope to do some damage. So if a player fails a combat roll, something happens in the fiction that prevents their attack from succeeding.

Maybe the environment is difficult: the ceiling is too low, the corridor too narrow, there’s an exposed beam in the way. Maybe the enemy parries, or they dive aside. Anything other than the PC just misjudging their swing due to incompetence.

Decide on why the PC missed, and narrate it.

The same goes for when NPC attacks miss the PCs: it’s because the PCs swiftly evade, or parry, or use their weapon to prevent the NPC from coming close enough.

Don’t roll for fluff

Sometimes a player will want to do something cool just because it’s cool, and not to gain a mechanical advantage. I know this may be a shocking idea. Maybe a player wants to swing off a chandelier during a bar fight, or leap across a table.

If that’s just fluff, for god’s sake don’t make them roll for it! If players have to roll for fluff, then they can fail (which will have consequences), so you’re encouraging them to not introduce excitement.

Consider this exchange:

  • Player: I run a few feet up the wall and push off it, my sword slashing down at the neck of the orc.
  • GM: roll for Acrobatics.
  • Player: I fail.
  • GM: you slip off the wall, and fall at the orc’s feet.

The wall jump didn’t give any advantage to the attack (if it did, it’s sensible to roll for it!), so here the GM punished the player for trying to make “I swing my sword at the orc” a bit more fun.


You are not the enemy of the players

The actions of the GM and the actions of the players often appear opposed.

But you are not the enemy of the players or the characters. It’s not the case that one side “wins” and the other side “loses”. Describe the world and portray its inhabitants genuinely, that is all.

Expect the unexpected

The players will do things you don’t expect, and that can be very scary!

It’s comforting to feel prepared. You can spend a long time thinking about everything the players could do, writing notes for every possible situation, preparing dialogue for all the NPCs… and then the players do something unexpected, something you didn’t prep for.

There are three ways to handle this, two of which are bad:

  1. Just shut it down. Tell the players they can’t do that, or introduce an impassable obstacle.
  2. Let them do it, but manoeuver the PCs back into your prepared events.
  3. Accept that your prep is not as useful as you hoped, and improvise.

Telling the players “no” or tricking them into getting back into your prepared storyline are not good things to do. Those techniques rob the players of agency, making them feel that their actions don’t matter.

You can never anticipate everything the players will want to do, so your prep will always be incomplete. And that’s just something you’ll have to accept, and become comfortable with.

Information and clues

Essential clues are guaranteed

If a clue is required to keep the session moving, do your best to make sure the players get it!

Make the clue available in a few different ways, and be prepared to improvise new ways if the players depart from what you expected. Ideally don’t make it require a roll; and if you do, have the player get the clue even if they fail, but maybe at a cost.

If the players completely disregard all the hints you’re giving towards this clue, and do nothing even remotely appropriate to get it… then you might have to make the clue optional and figure out how the session is going to proceed.

The characters live in the world, even if the players don’t

NPCs know things about the world—for example, a royal order of knights tasked with protecting the realm might know quite a bit about what various monsters are weak to—so PCs should too.

If there’s a piece of information that an NPC with the PC’s experience would be reasonably expected to know, then just tell the player it. You don’t need to write a book of everything each PC knows before the campaign starts, just bring things up in context.

And don’t require rolls for common knowledge! For example,

  • If the PC is a citizen of a certain country, they will almost certainly know the basics of its government, geography, famous people, culture, and so on, without needing to make knowledge rolls.
  • If a PC is from an area with a monster problem, they’ll know some tricks for dealing with some types of monster, such as how to recognise tracks. Though some of what they know may well be incorrect folklore, that’s fun too.


NPCs have hopes and dreams too!

A common mistake is to treat NPCs as only existing for the sake of the PCs. But the PCs shouldn’t be the driving force behind everything that happens in the world, that makes the world just feel flat and uninteresting. NPCs get up to stuff too.

Give NPCs their own motivations and concerns which don’t involve the PCs. If the PCs never showed up, what would Bob the blacksmith be doing with his life? Treat NPCs like real people, and the world will feel more alive.

Furthermore, most people won’t fight to the death. NPCs are the same! They will retreat or surrender rather than die, and this applies to intelligent monsters too.


You don’t need to know all the rules

Most RPG systems have a lot of rules. Even “rules-lite” systems can be difficult to wrap your head around when you’re new to them. This is a common source of panic for inexperienced GMs.

But don’t worry! If a situation comes up in play and you don’t remember the rule, you have two options:

  1. Pause play and check the rules.
  2. Make something up which seems sensible.

They both have their pros and cons. (1) means you get a definitive answer, but it’s not great if you’ll take more than a couple of minutes. Watching someone flip through a book isn’t that enthralling. (2) is quicker, but you could get it wrong. It’s ok to make mistakes, just check your rulings after the session, and adjust in sessions going forward.

Rules are not the Word of God

Sometimes you will disagree with a rule: you might think that it’s clunky, not fun, or just plain wrong.

You can change it if you want to.

But before you do, make sure you understand the rule first. Game designers are generally good at what they do, and games get playtested before publishing. If you’re confident you understand the rule, and you still don’t like it, go ahead and change it. But make sure you clearly communicate that to your players, and that you adjudicate your new rule consistently.

Make up rules when there are gaps

RPG systems have rules for situations the game designers thought likely to come up, but each individual game is a unique thing. Your campaign might go in unexpected, and unusual, directions.

For example, your players might end up becoming pirates, but there are no rules in the book for ship-to-ship combat. By all means, make something up to fill the gap.


Have breaks, arrange them beforehand

RPG sessions are usually multiple hours long. Three or four hours is common.

The longer the session, the more likely your players will need a break. Someone will need to go to the toilet, or to stretch their legs, or to get a new drink.

You could play continuously until someone interrupts play because they need to stop for a bit, but that’s not great. It puts pressure on your players, because people generally don’t want to interrupt everyone’s fun.

Alternatively, you can decide when the breaks will be, and let the players know in advance. Maybe you have a 15-minute break in the middle. Or a 10-minute break every hour and a half. This is good because it removes the pressure from the players. Sure, someone might still need to stop play before the scheduled break, but usually people will be able to hold out.

Silences are always longer than you think

A player finishes talking, and nobody else starts.

What feels like minutes pass. If you’re playing online and can’t see your players faces, you imagine that everyone is just sitting in silence at their computers, waiting.

Are they waiting for you? They must be! The silence is so long! Nobody knows what to do!

And then another player starts talking. In reality, 15 seconds have passed.

When you’re the GM, silences always feel like they last forever, even when they’re only brief. Before you panic too much, glance at the clock.

Finish early

As you get towards your scheduled end time, start to look for a good point to end the session. A cliffhanger or a bit of downtime are good for this.

You don’t want to have to choose between running late or stopping in the middle of the action. Much better to finish early.


I’ve found these (and more) resources useful as both a player and a GM: