Was at an LA premiere a few weeks ago, and the writer/director of the film was talking about his process. It included doing a lot of thinking about the project – months and months worth. During that time, he’d take notes and make short drafts. Then he’d outline the whole thing.
By the time he got to writing the screenplays initial draft, it was almost all there, missing only dialogue elements.
Each of us has a way of doing things that works for us. The best thing we can do is learn how we like to work, and make tweaks to our routine so that if frees us to create in our best possible way.