This blog entry from the Beaupre blog contains a substantial list of customer reference recommendations from the PR perspective.

Some of my favorites from the list:

Start small
One of the biggest faux pas? Going into a customer conversation with a laundry list of requests: quotes for news releases; speaking opportunities; case studies; videos; podcasts, etc. Don’t do this. Instead, engage in a thoughtful discussion and discover what appeals to them the most. Then work hard to make it a success in the customer’s eyes. Once you establish credibility via results, you can hopefully move onto a second activity.

Find the maverick
Some people are out to make a name for themselves and build their career. Being interviewed, quoted and featured in high profile opportunities appeals to these individuals. They are risk takers, have power within their organizations and agree to take responsibility for their own actions.
 
Small and involved beats big and uninvolved
Any customer reference is better than zero customer references. While a brand name is nearly always preferable, your communications program may still be well served by a smaller company eager for visibility.