Here's an good website that goes through how to find a responsible breeder.
Finding a Responsible Breeder
I think its most important that the breeder and new owner feel so comfortable with their decisions on placement that the contract itself is just a formality (they've discussed and come to agreements on all the points in the contract already). Contracts generally cover things like genetic health issues, training/care requirements, showing/trialing recommendations or requirements for puppies sold as show or working potential, basically the breeders responsibilities and new owners responsibilities. After that point its personal...depending on where priorities lie for both the breeder and new owner (everyone is an individual after all).