Improved relationships also improve the chance of getting referrals and future business. This is the key for a successful project. Without a clear contract neither you nor your client can be clear on roles and responsibilities, deadlines and deliverables, methodologies and measures. A clear contract is also a great aid to a good working relationship. The goal of a contract is clarity, not legalese.
Relationships are stronger when individuals take the time to know one another.
You will likely spend many hours with and around the client during the project. Knowing their likes and dislikes or interests could foster the working relationship further. This is more important to some clients than others. Make it a point to learn something new about the client in every meeting. Once you learn something new, keep track of that information in your contact manager, in your project notes, or wherever you can find it when needed.