This article by Lee Polevoi is about improving relationships with vendors, but it functions just as well as a how-to on improving relationships between contract partners. Our favorite tip:

2. Make Sure the Vendor Understands Your Vision and Goals

A vendor who “gets” your business is of far greater value than one who just goes through the motions of filling orders. Take the time to communicate your short-term goals and where you plan to take your business in the future. Invite their suggestions on the role they can play in achieving these goals. A trusted vendor will likely have unique insights into the industry and offer helpful feedback you won’t find anywhere else.

Keep your supplier updated on planned product updates or a new launch. Extend an invitation to attend strategic meetings or to simply tour the office to get a better feel for your business. Consider visiting their place of business and learning more about how they operate as well.