How I Prep
Jumping on a blog bandwagon pitched by Weird Writer of Roll to Doubt.
Before a Campaign
I always start with maps, usually one of the campaign overworld and one of the main tentpole dungeon. (It should come as no surprise that making maps is my favorite part of the hobby).
I usually try to begin with the minimum viable campaign seed of one starting town with basic resources and a couple stocked dungeon levels.
However, I always try to name distant sites, whether overland POIs or deep dungeon levels, even if I have no idea what they contain. Being able to reference these places on the fly does a lot for verisimilitude (c.f. Notebook Kayfabe).
Other things I like to have on hand:
- NPC names to check off, by culture/language. Coming up with these on the fly is tough.
- Encounter tables for the dungeon and each overland zone. I like to do smaller tables of hand-picked monsters where one of the results points to the OD&D wilderness tables.
- Dungeon dressing table with sparks for describing unkeyed dungeon rooms.
- Shitty, slightly misleading maps to use as handouts.
Before a Session
I usually procrastinate horribly before sessions, but I try to review where the players are & key a handful of dungeon rooms or hexes, especially if players have stated their intent to visit a particular site. With that said, I find that I have more fun & run better sessions when I don't stress & trust my capacity to improvise, discussed in more detail below.
After a Session
I think that writing post-session reports is a crucial part of prep. The practice of retrieving & summarizing a session consolidates it in my memory and strengthens my internal model of the world. In particular, I try to add the things I improvised to my notes as a seed for future stocking.
I inherited excellent character-tracking spreadsheets from my co-gm which I use to log PC experience and whereabouts.
Etc.
I used to think of prep through a naive mental model in which prep resembles architecture. You build the scenario, making it as sturdy and detailed as possible, then run it. If you're lazy or irresponsible, you can start using it before some parts are finished, but doing so is risky.
But some of my best sessions have been almost entirely sans pre-session prep. So now I think of prep more like gardening (or virtue ethics) -- the aim is to become the kind of person who can mentally model a vivid, consistent, interesting world as a basis for improvisation.
One needs fertile soil (e.g. following good blogs, reading varied books, playing in inspiring campaigns), & some regular discipline (developing a regular writing habit, tossing mostly bullshit ideas onto a web log every few weeks, writing campaign logs). But the garden has an autonomous existence, you can't control exactly how it will bear fruit.