I mostly make docs. I usually write a logline and treatment first. I find treatments very helpful -- I refer to my original treatment whenever I feel like the story has taken me astray. My treatments should help me clarify my approach to the story. I don't have to stick to the treatment to the letter -- but it reminds me of what I was after when I first came up with the idea.
For me, writing a treatment for a doc goes like this:
I figure out how long I want the doc to be, give it a working title, and then try to come up with a logline - the kernel of the story in just a few sentences. Then I spend some time writing a general overview of the main subject and how I expect/hope the story will unfold.
I ask myself a bunch of questions and write them down:
What's my angle/point of view?
How will I tell the story? What style is best?
Who are the most important/dramatic characters in the story?
What will the audience want to see?
Then make a list of locations, shots and/or sounds I'd hope to shoot, potential interview subjects, some of the questions I would ask my interviewees, and a summary of points I'd want to cover. After shooting and logging my footage, I have a good idea of what I've got. Keeping my treatment handy, that's when I create a 2-column script to organize the telling of the story. With documentaries, the script comes after you shoot. But a treatment is a very helpful first step before you shoot.
