References and Testimonials 

The best way to show your prospective customers what you can do for them is through testimonials or references from satisfied customers.  Ideally, the testimonials should come from companies that accurately reflect your customer's demographics.  To be effective, these testimonials must provide some form of contact information of those who offer them (usually, a name and a link to a website will work).  

 Make sure you ask for permission before listing your clients' name.  Most of the time, they will be more than glad to give you authorization, especially if you link to their websites.