Question: what are the characteristics of effective business letter?
Answer: It omits needless words. Keep the body of your letter at five or fewer sentences. ... 
It omits useless humor. ... 
It focuses on “you” (the reader) and not you (the writer). ... 
It is addressed to a real person. ... 
It has the appropriate tone. ... 
If and when necessary, it asks for the order. ... 
It provides your contact information.