I myself have been a repeating customer for many businesses which have served me really well. In business you have two main streams. One is the product and the other is the service. Some create products for the customers to serve them while some provide services directly to the customer. Some businesses combine both of them by offering you services to their products. Steve Jobs was one man who always focussed on giving maximum user satisfaction in the usage of any of the apple devices. The key here is the customer's satisfaction.
No matter how wonderful your product is, if the customer is not treated well when s/he comes to you for the purchase then you won't get the sale. Sometimes in spite of knowing that a better product is available somewhere else customers prefer to go back to those vendors who served them well during their previous purchases. This is quite natural though its against the logical reasoning of choosing a better product at a better price. The simple reason being sales do not happen over logic. Customers buy out of feelings and emotions. A very simple example for this is the purchase of clothes. Anything that you put on that can cover your body and give protection can be worn logically but the irony is people prefer to wear clothes in which they look better than what they really are. In fact wearing stylish clothes has got entangled with prestige issue nowadays. All these happy and pride feelings are just emotions without any mathematical logic. So whosoever can win the emotions of the customer through a charming service shall get the sale.
Service is all about a smile, respect and thank you. If you can serve the customer smilingly with complete respect to his/her choices and thank him/her for giving you the chance of helping him/her then you can be cent percent sure that the customer is satisfied with your service and shall come back to you for a repeated sale. Customer is the King and he needs to be served well and satisfied and he shall return to you soon and often. Shower some of your sales lessons on email@example.com