I do. I don't write it down or sit down and try to puzzle it out, but I do "rehearse" scenes in my head for a long time before I ever sit down and write them to figure out which version I like best, or what I can add that makes the story work better. I revamp based on what else I add in the heat of inspiration while I'm writing it down, and there's been more than one time I've ended up removing a scene because I just wasn't feeling it at all.