Learn the Customer

Every time youre with a customer, make it a point to learn something personal and professional about them. Dont allow your time together to be so focused on the immediate business opportunity that you miss out on additional, long term information. Its the long term information you gain that will help you retain the customer, and the longer you have a customer, the more likely they are to refer others to you.
When youre gathering information about the person, look for items that are of common interest to you both. These are the items that will help you propel the business relationship to the next level.