Strategies for World-Building

In an upcoming episode, we're going to talk about strategies for doing this on the page. Do you use a separate file for your world-building? How much of it do you actually do ahead of time? How much do you do it on the fly? I usually have something. I'll do some brainstorming. And mostly what I'm looking at is, you know, what... Usually, when I'm doing my world-building, there's some particular idea that I'm really excited about.