Three Tiers of Truth
The DM is asked a question like, for example: what’s in the office?
- Look in the prep. Maybe this room is in there and the text says what is canonically in there, and you’re all set.
- Otherwise, maybe you have a rule (“default offices have a stapler, a typewriter, a visitor’s chair” etc) or mechanic (such as a random room content table). Use that.
- If you don’t have that either, make something up. Try to make it something that won’t help or harm the player characters too much. It can be evocative and build mood, but shouldn’t be 20 angry beholders (or 20 free healing potions). Don’t feel bad: allowing DMs to start small is how we get new DMs. But, patch the hole, or this category of holes, for future sessions. Then over time your DMing will get more and more solid♥︎.
Always work in that order, top to bottom, only falling to a lower tier of truth when you have to.
A campaign that’s built on all T2 and T3 truths isn’t as engaging as one that has some solid T1 framework in there (in a cloud, bones of steel), but as you patch holes (as T3 instructs you to) feel free to patch them with mechanics and general solutions (i.e. T2 truths). That’s you building a DM’s toolbox.