First I start with a CHARACTER LIST - which lists every conceivable description about them: physically, mentally, and emotionally. I write down every last detail that I can think of whether it's pertinent to the story or not.
Next I add my PLOT DESCRIPTIONS - which lists every known feature about the locations geographically.
Then I write a PLOT SYNOPSIS (1-3 pages) detailing everything thing that happens in a nutshell.
And then comes my SCENE LISTS - where I list every single thing that happens in the story. I have headers for ACTS 1,2,3.
I can get a bit anal when it comes to plotting out stories before I write them, but that's because I need a specific guidelines before writing. Otherwise I feel I'm writing blind.