How do you prepare? How far ahead do you prepare? Could you run the next session right now? What about the one after that? After that? If stamina and the time it would take weren't an issue, how many session's worth of content would you feel comfortable going through?
Personally, I tend towards vague preparation. I don't like to lock myself down to "this encounter, with these NPCs, at this time because reasons" unless the players have given me very good reason to expect that (i.e. they're attacking a corporate building end of the first Matrix style.)
No, instead I focus on story aspects. I try to take in my characters, and their players, and think about the story. I try to come up with plot events that could focus around each of them, and from those events I come up with bullet points that are key to how said story will go. If a plot needs more - say a stat block for a key NPC or item - I can make that. Mostly though, I prefer to have tent pole moments.
Why do this? Because if I have the key points for each of the plots written down I have things to work towards, but still leave maximum flexibility for my players. If they go off and make their own content...well, it's no big deal to me. If they don't, I grab one and lead them to one of the tent poles and see what happens.
I can revise these as things go along.
Then, before a session, I think about what - if anything - in specific I want to do that session. This is based largely off what the PCs were doing last session and how it could lead into this one. It also depends on what plots are active, what is going on, and who - if anyone - had the focus or lack thereof for most of the previous session.
The details wait until just before they're needed. The general shape is scoped out well in advance. Sometimes the notes are very rough and vague. For example, here is what i have for one of the players in my current L5R game.
- What it can offer
- The heavy cost
- Finding a balance point
- Teacher or Student?
- The Big Decision
None of these tell you much about what is going on. On its own it is hard to discern. If I tell you that this plot focuses on a PC who needs to redeem an awakened magical sword and things make more sense. And yet, I can still have this here because there are no spoilers for the player when/if he reads this post.
These points are things that need to be there for the story to work. But they also give me guide lines when I have a quiet moment and this PC is available.
So, what do you do?