One of the things which puzzles me is how a writer works with another writer on the same book/episode/movie. Is it like a round robin? Does one writer write an entire rough draft and the other suggests changes as they read along?
About collaboration — Everybody winds up devising his or her own method. I don’t know what other writing teams or groups do, but around here, this is how Peter and I manage it:
Assign a project leader. Which of you is better at this particular kind of work? “Better” being a very specific value judgment that varies from project to project. It can mean: Who does this kind of work faster? Who does this with less day to day effort? (Because you have to factor in the wearying effects of long-haul projects.) Who does this work with more insight / nuance / depth ? Which of you has been doing it longer? And sometimes, who has more credential? — though this often holds less weight inside the household than it does outside. One of us may know that the other is better at a particular kind of storytelling even though that one doesn’t have as much formal credential as the other. (Also sometimes affecting this choice: Which of you does the company you’ve contracted with think is the project leader? — and here issues of credential may be involved.)