I've had to take a different approach to this book and do some outlining, as well as a good amount of research notes. But usually, I don't plot or outline. I don't like it; I like finding out in 'real-time' all the little surprises that the characters discover. When it comes to ideas, I don't sit down to write until I have some room to run. Ideas, for me, have to bounce around in my head for a little while---could be weeks, months, even years---before I even sit down to start writing the first draft. I usually know something that's gonna happen in the beginning, I know something that's gonna happen in the middle, and I know something that's gonna happen in the end. Everything in between, I am completely in the dark, and it's then my job to take my characters and my idea and find out what those answers are.
As far as writing the first draft and how 'clean' it should be: Look, it's called a first draft for a reason. Nobody should be reading it but you. The point of the first draft is to just get the story down. You're gonna have to edit, anyway. I spend about four months on a first draft and then I spend another eight months (at least) going over the story, cleaning it up as much as I can. So when it comes to your first draft, write wht comes to mind, get your thoughts down, throw everything you can at your manuscript, and then worry about cleanliness and perfection later. That's what rewrites and revisions are for. If you always try to blow your wad on your first draft, chances are, you're never gonna get anything done.