When it comes to publishing contracts, be careful before you jump in with a self publishing company. Read any and all contracts and know what you are signing and who you are dealing with. I have been watching as new consultants sprout up everywhere, with people who have done one book -- their own -- and then suddenly they are doling out publishing advice. I've also seen several people who have been laid off or fired from the traditional publishing world, where they performed one part of publishing, who are now opening up their own consulting firms. So dangerous for you! They often don't understand the whole-picture hurdles and, conversely, the special opportunities in the self publishing world.
If you are considering working with a self publishing company, read the contract, look at the books they have already done, request a detailed proposal or scope of work; also check references. If any vendor holds any rights to any aspect of your book, question it and make darn sure you understand the answer! Don't settle for commonly found lines like "You own 100% of the rights to your work." You want to know who owns the layout and design of the book when it's done. That's a good place to start questioning.
CAUTION: A check or payment is an implied contract. If you don't sign a specific contract, but you gave them a check or paid them anything, you now have a contract with them anyway. One additional note regarding contracts, don't rely on your regular attorney to know what the terminology means either...you need an intellectual property lawyer (and you want to make sure you know what the terms mean before you talk to them, too.)
Protect yourself by arming yourself with lots of information -- and make sure you really UNDERSTAND everything.