Develop self-confidence by winning bigger than you expected. Self-confidence is attractive. Customers are especially attracted to it. Get to the point where they consider you a resource of information rather than a salesperson. Tell them one, and they tend to tell you one back.
Stories are personal.
Stories are revealing. Tell how do you do it with them. Get them leads or put them in front of contacts that might lead to business for them. Part of the relationship building secret is to break the ice. Nothing like going to the same college, or growing up in the same town, or having worked for the same company.