What does your session prep look like? How much time do you put in session to session? How much time goes into your game every day? What things do you need to have down and ready before you feel comfortable starting to run your game?
I tend to do big planning in bursts. I'll plot out an area, a plot line, or a few sessions of things I want to happen - or NPCs the PCs will meet - and then I go from there. Before a session I'll put in some indepth focus time for what I know is coming up, but most of my broad strokes planning is done well in advance of the actual session where things happen.
The broad strokes are also the big thing I need to have ready for a session or I feel out of sorts for it. I need to know where the major pieces are moving - or trying to move - and why. If I have that I can run the session, improv what I need to, and let the players take the reigns a little more. Without it, and I just kind of feel lost.
In regards to those broad strokes I more need to know the major NPCs and their plans. The environment around things I tend to not care too much about it. In general I'm not a very visual person and have a hard time imagining environment specifics. My games are better when I put the needed effort in for those visuals, but I don't need them to run the story.
What about you?