Usually store ideas and scenes in my noggin for a really long time, let it gestate like some mental illness or virus. Then I write out a vague outline on a single scrap of paper to see if the general structure is there. I won't start a script until I know the title, have a good opening, and a definite ending. Then I find mood music, or make a mix-cd of what I'm going for, then play it on repeat indefinitely. I then bust out Final Draft 5 and go to work, as scenes and ideas often change and take on a life of their own as the work progresses. The work is very concentrated, all night and all day for a couple weeks max. Then months of sloth and depression. Rinse. Repeat.