One of the people I most admire is Vinod Khosla. He got Sun Microsystems one of their first contracts by camping out in the lobby of a customer (they wouldn't take his meeting) and meeting them on their way out daily to tell them why they should do business with him. He did the same thing to get into Business School at Stanford. He was rejected but just came anyway and after hanging around for two weeks, somebody dropped out and they let him in. Persistence pays.. but yes, the trick is to do it in a respectful manner.