One of the most commonly recognized list of admonitions for good customer relations is that developed by Frank Cooper, from his book The Customer Signs Your Pay Check
Ten Commandments of Customer Relations
1. The customer is never an interruption to your work. The customer is your real reason for being in business. Chores can wait.
2. Greet every customer with a friendly smile. Customers are people, and they like friendly contact. They usually return it.
3. Call customers by name. Make a game of learning customers' names. See how many you can remember. This is a valuable habit.
4. Remember--you are the company! In the customer's eyes, you are as important as the president of your company . . . probably even more so.
5. Never argue with a customer. The customer is always right (in his own eyes). Be a good listener, agree with him where you can, and then do what you can to make him happy.
6. Never say, "I don't know." If you don't know the answer to a customer's question, say, "That's a good question. Let me find out for you."
7. Remember that the customer pays your wages. Every dollar you earn comes from the customer's pocket. Treat him like the boss. He signs your pay check.
8. State things in a positive way. Choose positive words when speaking to a customer. It takes practice, but it is a valuable habit that will help you become an effective communicator.
9. Brighten every customer's day! Make it a point to do something that brings a little sunshine into each customer's life, and soon you'll discover that your own life is happier and brighter!
10. Go the extra mile! Always do just a little more than the customer expects you to do. You will be richly rewarded for this habit!