Get through a draft as quickly as possible. Hard to know the shape of the thing until you have a draft. Literally, when I wrote the last page of my first draft of Lincoln’s Melancholy I thought, Oh, shit, now I get the shape of this. But I had wasted years, literally years, writing and re-writing the first third to first half. The old writer’s rule applies: Have the courage to write badly.
Sometimes it helps to pick out one person-a real person you know, or an imagined person-and write to that one.