One way of making your products or services - and your company credible is by establishing yourselves as experts in your particular field. Publish white papers, or articles on the web showing your grasp of your corner of the world. Attend tradeshows, and work with the organizers to get speaking engagements. Publish articles that add to the knowledge base in your area.
Above all, when meeting with a customer, show your knowledge in your product area. Every good marketer should know his or her product inside and out. Make sure that there are no questions that you can't answer. If you do get stumped, go back and research the question - and get back to that customer as quickly as possible. This is the way to win in today's competitive marketplace!