Preparing for a session is hard, not least because it’s rarely clear what a DM needs to prepare. If you spend hours mapping out the sewers where bandits are hiding, you can be sure that the players will instead look into the stockholders of the company from which the bandits stole. If you build two armies so the players can weigh them both and either join one or stop the battle, the party will instead leave the country and explore another area you offhandedly mentioned once. Even if you assume that the players are going to run off and do something unexpected and prepare for everywhere you think they can go, one of them breaks into an inaccessible building and murders the most important person they can reach just to see what will happen.
All of these happened to me. The army one happened twice. There’s a teachable moment there.
There’s a maximum amount of preparation you can commit to a session because there’s a maximum amount of preparation the players will tolerate. Gamers have a sort of natural entropy that causes any plans or expectations to break down over time. It’s one of the reasons a 13-episode season is so hard, because it’s never clear from minute one what’s going to happen in a given week, much less five or ten weeks down the line.
The natural response is to stop planning at all, or at least that was my response. That is, trust in your own improvisational skills to deal with whatever the players want to do, and if you have an overarching plan you can lay seeds or nudge things along the way so it looks like you know what’s going on. However, right around that time we started using software to track combat statistics, show backgrounds and NPC portraits, and so on. This meant that either I took quick breaks before anything new happened so I could frantically search my pictures folder for something appropriate, or I had some idea of what was going to happen before the session so I could get things ready and let the game flow. Even my plan to stop planning was subverted. Meta.
This approach doesn’t work for all GMs. Some prefer the heavy planning or think they’re not good at improvisation. That’s fine, but the DM isn’t the only person in the room. Lately I’ve been leveraging something I’ve stolen unabashedly from story gaming in general and Left Oblique in particular:
slave labor asking players to do some of the design for you live.
Imagine your players walking through a dungeon. Say, for the sake of argument, that you really wanted them to negotiate with the thieves’ guild this week, but they sprung a good old dungeon crawl on you by biting on a hook you hadn’t expected. You don’t have any dungeon prepared, much less the sorts of monsters or traps or treasures they might encounter. So when they open the first door, don’t wait for them to ask “What do I see?” Instead ask them the same thing, “What do you see?”
This isn’t laziness or a saving throws (well, not exclusively), it’s an opportunity for the players to participate in the session design. Some players will panic and shut down (see the aforementioned “think they’re not good at improvisation”), but somebody might jump at the chance to explain how they see the dungeon. In between you’ll likely find the player who asks questions rather than making statements, like an unprepared high school history student:
“Are there monsters in the room?”
For the sake of argument let’s say you haven’t decided what sorts of monsters live in this dungeon yet. “No.”
“Is there anything on the walls?”
Right away, there’s something you may not have considered even given time. If you’re still puzzling out what lives in the dungeon, you certainly haven’t made it to their interior design. You could say no, but the point is to have everybody build the room instead of building what the room is not. “Yes, uh…tapestries.”
“Great! I steal them!”
You can deal with the logistic of carrying carpet if you want. The point is that now you know your monsters live underground but appreciate finery. They might have made it, they might have stolen it, or they might have recently taken over the area and haven’t bothered to take down the old trappings. Also, a player feels rewarded for speaking up and asking about the room, and players will do something again if it gets them a reward. They’re a lot like horses that way.
“What about bones, are there bones lying around?”
Again, if you say no, it doesn’t mean anything. But if you say yes, your monsters can be carnivores. Pairing discarded, gnawed-on bones with wall tapestries makes for a very interesting monster. “Sure, why not.”
“Great! I steal them!” Because players are creepy.
Bit by bit, a picture starts to form. “Is there any lighting?” Do you want your monsters to need light? “What’s on the tapestries?” What sorts of things might the monsters want to depict? “What are the floors made of?” Are your monsters craftsmen who like making their place attractive, or do they care so little that the floor is rough and jagged? With each question you not only build the room but build the creatures who live there. By the time you’re done you have cannibal artisans who worship the moon, the dungeon feels unique, and the players are interested in meeting the inhabitants. And you haven’t prepared a thing.
(If you’re still worried what these monsters could be, just grab something close and tweak it. Heck, grab something far away and tweak it. Since the players were going to fight ninjas in the thieves’ guild, they’re fighting ninjas now. Just change their presentation to something that fits the theme you’ve developed, like sneaky nocturnal gnolls. You have all week to redo the guild into a Mafia hangout instead. Work with what you have.)
If this example sounds trite and unbelievable, it’s because example play always does. But it’s pretty close to how things do pan out. You might make it to the fourth room before anybody asks what the walls or doors are made of, or how the lighting works, or how the place smells, because it’s not important to the players. And that’s another trick to this method: you don’t spend hours writing and reciting a tortured description of the dungeon when all the players want to know is certain bullet points. If they don’t ask which way the door hinges swing, and you don’t have a reason to discuss it, don’t bother. You’re paring the game down from the realistic but labored descriptions to just the bits that make it fun.
If it sounds boring, that’s because it’s for a first attempt. When players aren’t used to coming up with things on the fly, expect room design to read like a game of Twenty Questions. Once they get their footing and understand more about what they want to see and what works with the game, they’ll get more bold and you’ll find them starting to surprise you. Maybe you didn’t think your orc base would have a spa, but now it does. Roll with it. If they start going too far-flung, you can always rein them in. Or don’t; it depends on the game everybody wants to play.
Of course this isn’t just for rooms. I’ve had success with asking players to design NPCs on the fly. The simple question “So, which crew member have you been spending the most time with?” gave me an overweight elf hiding his race, a gnome shipwright with a bad case of hero worship, a pirate with a crystal hook for a hand, and a cat that harasses the party’s cannoneer. That’s four NPCs I didn’t have to design, giving life to the boat rather than keeping it filled with faceless mooks. It also gave them some attachment to the PCs so there’s some interest in each. Now instead of “a crew member is missing”, I can say “Bobathan Bobert* has disappeared” and the players not only know who that is but that they’re suddenly out a carpenter. It increases investment, one of the purposes of not only gaming but of media in general
There are situations where this won’t work, or where you don’t want it to. No player will begrudge you if you opt to design the party’s patron or the campaign villain on your own, and if you leave every bit of design to the players they might wonder why they need you at all. But when you’re stuck, or out of time, or just want a little punch to keep things dynamic and interesting, ask the players to do some of the work for you. You’d be startled at the things they come up with.
* — For reference, his friends call him Sal. Because that’s what you get when you try to name an NPC “Bob”.