Phil Edelstein and Chris Fernandez (client and designer) have written a sharp article explaining how they made their relationship work. They divide their process into stages, and I especially appreciate Chris describing how he built the relationship even before he got the project.
“Even before the project went to RFP (request for proposal), I used Twitter to maintain a connection and begin sending Phil relevant articles with ecommerce best practices and examples, understanding visual hierarchy and user interface design, and the all-important, if not terribly sexy, checkout flow design. Happily, he seemed to accept them rapturously.”
You can even do this to build credibility within your organization (if you’re an innie.) I used to send around emails to the UX team at eBay, and not only did we engage in great discussions but it helped the other teams respect my team and our opinions.