Prep Dictates the Game

Preparing for a session is one of the key differences separating the GM experience from the other players. Most systems assume the GM will spend some amount of time before a session planning what they might present to the players: creating NPCs, designing combat encounters, writing flavor text, thinking up story beats... But just as important are the things the GM chooses not to plan in advance.

The Dragon Casts a Long Shadow

Like so many areas of this hobby, the closest thing to a standard we have has been set by Dungeons & Dragons (for better or worse). D&D is a system that expects a lot of prep work every session, especially for combat encounters. With such heavily tuned mechanics, game balance plays a larger role than most other systems, and so properly adjusting the difficulty of combat requires a lot of attention. This mentality has been extrapolated to other parts of the prep process, and reinforced by the way modern D&D adventure supplements have been presented.

While it is possible to run Dungeons & Dragons without much preparation at all, there's a reason most GMs will put that degree of effort in up-front: The experience. Not just their own experiences of feeling prepared, or being the world's architect; but also the players' experience of exploring a world that feels concrete. When a location or a plot point have been concocted before the players reach it, they feel like they're exerting agency on a world that is more "real" than one the GM is coming up with on the fly. We could call this "immersion", if that weren't such a loaded term already.

Find Your Focus

The content you prepare will dictate where your attention is during the session, which in turn guides the direction of the adventure and story. If you focus your preparations on contingencies for the actions your players might take, then you'll inevitably be caught off-guard when they do something you haven't accounted for. This is where railroading comes in, as some GMs will deny unforeseen player actions because they fear being unprepared. When we don't prepare for a certain course of action, that actually opens up the possibilities of what players can achieve.

There are plenty of different approaches to prep work. Many modern scenarios will present a location in its default state, giving enough context for the GM to respond dynamically when players disrupt the status quo. Another approach is the ever-popular roll table, a collection of pre-generated events, obstacles, and descriptors to bring into existence as needed. And in the more narrative, collaborative space is the "writing room" approach, where all the players participate in setting the scene and introducing complications.

For the most part, any of these approaches can be applied to any system. Some games will certainly present a particular prep method as the "intended experience", but as all things in TTRPGs, this is a guideline that we are free to adjust (or ignore) at our own tables. It's totally possible to run Blades in the Dark as a dungeon crawl with a map and predetermined enemy locations, or play a Heart campaign purely generated on-the-fly with roll tables (even if it makes the developers wince when they hear about it).

A Case Study in Mysteries

Let's look at an example of how prep contributes to a game's feel, with two eldritch horror mystery systems that call their GM a "Keeper": Call of Cthulhu and Brindlewood Bay (yes, I know there are other contributing factors here, just hear me out). The average Call of Cthulhu scenario is dozens of pages long, even without handouts. They expect the Keeper to read through all this content in advance, since running a standard session requires knowledge of timelines, locations, NPC motivations and actions, and clues (including where they are and how to obtain them). In contrast, Brindlewood Bay mysteries are rarely more than two pages, and can be run without any preparation at all. You have a list of clues (which can be found anywhere), NPCs are summarized in two sentences, and locations are given a basic description in a single sentence.

To be clear, neither of these approaches are better than the other. This isn't a lesson in "less is more", or "more prep makes a better mystery". These systems have such wildly different preparation expectations and standards because that's what dictates the experience. Call of Cthulhu lays out a mystery for the players to solve, almost like an escape room. This will have the players writing down notes and deducing where to go next or who to question, with just one correct answer that they either arrive at, or die trying. Brindlewood Bay gives the players the building blocks to create their own solution, finding the fun in creating connections that didn't exist, but feel satisfying when linked together. Players know there's no single answer, but are still motivated to uncover the story that they create as they go.

Now here's the kicker: the scenarios can be used in either system. A confident Keeper can take the Brindlewood Bay mysteries and run them in Call of Cthulhu, with or without the extra prep time to connect the clues in advance. And the prescriptive Call of Cthulhu scenarios can be dropped into Brindlewood Bay, maybe foregoing the Theorize Roll to determine if the players found the right solution.

Find What Works for You

As always, there's no wrong way of doing this. "Low-prep" is often toted as a selling point for some systems, but I think it's more of an indicator to the style of game. I tend to adapt my prep methods to whichever game I'm running, which ranges from nothing at all, to a single A6 page of locations and obstacles, to a network of notes and maps to hand out to players.

What matters most here is what you have fun preparing. GM burnout is a real thing, when it feels like a chore to get everything ready for the next session. If you find that's happening to you, switch things up with a new preparation approach, you might find something that works better for you!