Basically when I come up with fanfic ideas, I usually listen to my mp3, and the ideas come as a kind of AMV that's going to the rhythm of the music. Usually if I like it enough, I'll roll with it, and eventually they become fanfic ideas.
Before I start writing a chapter, I first write a small character sheet for whatever character appears in it. Then I go on to write a synopsis of the chapter to give myself a general idea of which direction the chapter's gonna go, something like "Character A wants to do a thing, but Character B stands in his way! Will he overcome the challenge?".
I usually listen to youtube or Pandora while I write. Recently I've been listening to The Beatles station while writing. For research, I keep wiki pages up in case.
SUPER POOPER SCOOPERS ARE JUST LEGENDEH!
Would that it were so simple.
Stream of consciousness. Write a ton of shit, break it up, develop it, polish it, and turn it into chapters.
"For all those whose cares have been our concern, the work goes on, the cause endures, the hope still lives, and the dream shall never die."
I suppose I don't write all chapters concurrently for every story, just the episodic ones. The more direct plot ones I guess I just outline in advance and then write mostly linearly. It's just that more of my longer fics are episodic.