Thing Six: Getting a contract in hand is NOT the end of the job. It’s the beginning.
Now you get to work with one or more editors, copy editors, and proofreaders. Multiple times.
Thing Six-A: Be aware that you are NOT required to do everything, or even anything, the editors say. But you better really be confident you’ve done it exactly right, because these guys are usually way more experienced than you are and know what they’re doing. (Not always. But mostly.)