Answer:
The essential qualities of a request letter are the same as any business letter, clarity and conciseness. A letter of request should be written in a way that directs the mind or the reader to the result that you expect from your request. This is done by using the preferred order of information of a standard business letter:
first paragraph, state why you are writing the letter.
second paragraph, state the information supporting your request. Provide the information necessary for the recipient to know what specifications or directions may apply to your request. Don't use more than one paragraph unless absolutely necessary; if there is a lot of related information, use bullets if possible.
third paragraph, (known as the call to action paragraph) tell the recipient what you want them to do, giving them any information necessary for them to follow through (deadline or pertinent dates, phone number, email address, third party, etc.). Always thank them for their time and effort.