Strangely enough, when Erica and I write, we do the same thing that I do as a solo writer. We prewrite for hours and hours, figuring out the smallest details which we need to handle. Then, after that's done, we write fast and furious until the project is done. I don't even want to know how much time we spent narrowing down what we were going to change in this revision only to crank out the revision in less than 48 hours.
Oh, and in case you're wondering...we had a great time doing it.