Creating stories with someone can be one of the best experiences for a writer or one of the worst. In the past, I provided some prerequisites and some practical considerations. This time, I'd like to offer a few suggestions on how to make the day to day effort go smoothly.
Brainstorm with each other. Ever wonder why humor writing is done so often in teams? One reason is because each person needs an audience to know if his/her jokes are working. All storytelling benefits from a sense of audience. But beyond that, teammates with the right chemistry will egg each other on to stuff that is bigger and wilder than either would be able to come up with alone.
Pitch to each other. One of the best ways to understand the merits of ideas, premises, and concepts it to try to sell them. I prefer doing this with as few words as possible, and then having the other person react and ask questions (beginning with clarifying questions).
Help each other out. Whether it is research or a nagging question or a choice in a story's direction, the writing partner should be the first person to provide new options, find answers, and help to clarify concerns. This needs to be done in an ego-less way. In other words, respect the instincts of the other person and don't jump in with your own version of what should be in the story. Save that approach for something other than a help session.
Cheer each other on. When the work is being composed, your default response to a partner's offerings should be positive, not negative. Enthusiasm, not disappointment. Trust that the seeds of something wonderful are in the shabbiest of drafts. There will be times to be realistic. Most of them come during the revision process.
Appreciate the person you are working with. Be polite always. Be generous. Take time for your partner and, if nothing else, mark off partner celebration days on your calendar. No one can bring to your work what this person can.
I love collaborating. The talents and perspectives of other writers delight me. And the right collaboration is less lonely than working alone. That's nice for a change.