Testimonials have always been important, but even more so today thanks to the Internet. People have become conditioned to look for reviews, Angie’s Lists and five stars every single day as they surf around, even when they are not buying.
Your internet presence is more of a marketing challenge than your personal challenge as a salesperson ( unless you happen to manage both), but as a salesperson, it is always good to have a group of people in hand who are willing to endorse your work before a prospect asks for them.
Most people like to endorse good work, so your best clients will be happy to do so, but it is best to casually ask them in advance rather than blindside them when the request comes up.
Even better, if you can get a quote from them that you can use in your sales efforts, you can use it even when an endorsement is not requested. This is a very, VERY powerful way to improve your chances of standing out in a sales pursuit!