Know those 'unwritten' expectations
Customer satisfaction is a very subjective thing to measure. It really is a matter of perception and experience.
Source: Sales consultant/author Bob Hooey
If you meet or exceed the "unsaid-unwritten" expectations of your customers, their perception will be a positive one. Fail to meet these expectations, and you will find them less than satisfied or happy with you.
One method to make sure you meet or beat these "unsaid–unwritten" expectations is to do your homework or research. Often, within an industry there are certain "unwritten, but still valid" expectations, which serve as the norm. Make sure you know what they are and use them as the bottom line in your service and performance.
If you want to succeed in gaining their repeat business and loyalty, make sure you go well past the "normal" expectations.