Specifically state what it is that you are applying for or interested in applying for (e.g., the position, appointment, student or other visa, extension on a deadline, loan, credit card, etc.).
Identify the reason that you are applying. Be as specific as possible.
Give the reasons that you feel you merit or qualify for the position or object/thing you are applying for, if applicable (e.g., your goals, experience, qualifications or accomplishments, positive traits, and so forth).
Identify what you hope to accomplish by sending your letter and the action you would like the recipient to take.
Indicate the date by which you would like a response to your letter or by which you would like the action to be taken.
Refer to any other documents you have included with your letter, such as application or other forms, letters of recommendation, resume, examples of your work, etc.
Include a request for any information you would like to be sent, if applicable.
Include your contact information, such as e-mail address or phone number where you can most easily be reached and the time(s) when you available for calls, etc.
Close your letter by sincerely thanking the person for his/her time or for any assistance he/she can give you.