Use good human relations skills as you write.  Treat the reader with respect.  Demonstrate that you care about the reader as you write.  When talking with people face-to-face, courtesy and consideration are necessary to develop and maintain goodwill.  The same or perhaps even greater concern must be evident in written correspondence since only the written word conveys the message – a smile or friendly gesture cannot be observed.

Courtesy also means being considerate.   If a person is asking you something, respond.  If you are unable to give a positive response, explain why.  Explanations let other people know you are sincere.