Passive Guy at his wonderful blog www.thepassivevoice.com has a great article called “How to Read a Book Contract–Contempt.”
A must read for anyone thinking of going into a contract with a traditional publisher. After a hundred plus book contracts for my own work over the years, I can tell you for a fact he is spot on the money.
My advice: Simple. Do not go into a negotiation with a traditional publisher over a contract without an IP lawyer on your side. Critical these days. Flat critical.