My organization is pretty straightforward, with some divergence between in-person and online-only games. I only do homebrew, so
Everything is kept in electronic format, most recently moved to google docs because my gremlins made fun of my old-fashioned ways at the urging of my loving, D&D-playing children.
I do a lot of longer term and big-picture planning, so that I have material for when I'm improving. So I have a several documents with different parts of that. Usually a geography one (homebrew worlds) that is likely better labelled with something else as I will also have common inhabitants, points of interest, and such. Or even things like "random things to stumble across exploring the jungle" charts.
I have a one on character arcs. For me I try to weave in bits of different character's arcs throughout the whole campaign, so this this not just plans but also reminders to me what has actually hit the table so I can make sure it stays consistent over time. Plus I do "Schrodinger's Plots" - nothing is true until it hits the table, even if I had it planned long ago.
But my most important is my Session planning doc. I do a new one for each session, but I start with the last one. First page of it is my character run-down - skills/abilities they have, allegiances, rivals, hatreds, etc. - basically a quick summary of the connections for a character and what they do so that when I'm planning sessions I can look through and say "oh, I should throw in some traps so the rogue who took expertise in finding and removing them gets some spotlight on that" or "hmm, can I tie this into one of these organizations?".
Next is a "things to remember" for me. Like "2 days left before the deadline" or "tell Brandor about the dream he has", "thunderstorming", or "they are still under the effects of the curse". (All names silly in this post, not in actual play.)
After that in my session doc is a recap that I read at the start of the session - while it's usually a capsule of the previous session, it may also contain information the characters know and should be top-of-mind for the players. "Baron Bahd Guie, the one who kidnapped Brandor's mother, is leading the delegation you are trying to infiltrate."
I'll have a short bullet point of various challenges I'm expecting, more of an overview that I can jump to to keep my eye on stuff - oh, I use the various Headings to create a heirarchy, and use the navigation bar to jump back and forth.
Then I'll have details on the various scenes/locations/however I need to organize what's next.
I'll have various cheat-sheets embedded in this, oft times from other documents. For example for a city I might have the quick overview, a racial breakdown, and lists of names for the common races so I can pull out NPCs quickly. For things I give a reasonable chance of turning into combat encounters I will have a stat block right there.
For online games I'll likely have less overview since I can pull up any of the documents quickly. For in-person games I print it out and run from that, trying not to bury my nose in technology while running unless I really need to.
For both I'll have images of people, places and things ready, and for in-person I'll have printouts of magic items they find to hand to them, also with images. Online-only I've recently started doing a shared party treasure google doc that I can copy things into and they can split up and everything as they want.
I have what I call the dramatis persona, but really it's just lists fo the various NPCs, broken out in a heirarchy. For example movers and shakers for a nation will be listed for that nation, which local folks are listed in whatever settlement or organization they are. But really this is a place I can take NPCs that I worked up in the session document (below) and cut-n-paste them to to have them findable later. They include RP and relationship info as well so that stays consistant when they meet NPCs sessions later. Mind you, an NPC dragon might have the map for the lair that they snuck through - the idea isnt' to spread information around, it's to make it manageable.
I also have the generally labelled "archives" which is everything else I want to keep from session documents but isn't around a NPC, or is around too many of them. Though some things might get added to the other documents - a quarter of a city, expanded out in feel, inhabitants, and a couple of shops during play will have that tossed in the geography book.
These various books start mostly empty - at the start of play I'm looking at high level details only to introduce it to the players, do a sessions 0, build characters and connect them to the world, and figure out the start of play. So character connections and starting areas and plots are the first details I'll have in there.
Oh, I have worlds that move on even if the PCs are not paying attention to sosmehting. This goes hand-in-hand with having more hooks then the PCs can follow, and being willing to improv when they (regularly) make up their own directions. So having this much surrounding information helps me keep everything feeling like one world and having what I need to improv - because I know what's around, who's keeping an eye on whom, and what can happen.
