19. When you have bunnies, do you sit down and start writing right away, or do you write down the idea for further use?
This completely depends on what the bunny is, how much time I have to work on it at the moment, and what kind of fic it will turn out to be. For example, I got an idea for the next who_contest challenge last night, and though it was time to go to bed, the challenge was short enough (<500 words) that I got half of it done before turning in. I finished the rest of it this morning. I think I'm a little too rational to get so excited about an idea that I have to sit down and start writing no matter what.
Most ideas for longer works end up in my "Story Ideas" document, simply because I already have two unfinished long works and I don't need to start yet another one. It's a little disheartening, because there are new ideas that I want to work on and I feel like I'll never get to them because of RL and fics that in line before them. I do try to write good descriptions of the ideas and update them with new ideas that pop into my head, so that when I do get to them, I don't forget some of those neat little things that I think of sometimes. Short work ideas usually get attention a lot sooner than long work ideas, because I can work on a short story for a few hours (days?) and actually finish it without interrupting other works too much.
I think the last time I had a really invasive bunny, meaning something that really obsessed me, it was The Actor, and even then, for the first half of it, I was alternating every night between writing it and writing the other long fic. When I started getting close to finishing it, I then switched to working on it exclusively.