You need a good editor and book designer. You're paying for his or her advice, so take advantage of it and don't second-guess your bookmaker's expertise. Do your part. Submit clean copy or disk files. Give clear and specific instructions where they are important to you.
Return proofs promptly when asked.
Don't edit or rewrite after the book is set up. If you follow these simple common-sense rules, your project will proceed smoothly with no nasty surprises, and you'll find the process to be both exciting and rewarding.