I wrote my first novel during January through April of 2011, and I came to associate writing with winter, for some reason. There wasn't much to DO outside and such in the winter, and my classes weren't *that* hard last year, so I was writing at least 5-6k over the course of every weekend towards the end. I'd wake up and it would be cold outside and warm inside and it felt perfect to stay in and write. I had such a hard time getting even 20k out this summer. Definitely trying to break the only-writing-in-winter thing. But at least winter's coming, so maybe that'll help :D
The last one I can think of is music. I'm obsessed with playlists for my novels and I can find hours searching for new songs that fit perfectly . . . when I should probably be writing :P I was thinking of sharing the playlist for my current WIP on the blog once I finish the first draft. Though it is still subject to change, so I'm not sure.
Do you have any writing superstitions/associations?