A letter of request is a letter in which one person asks another person or group of people to grant a specific demand or respond to an inquiry or appeal. Request letters should be brief, polite and to the point.
Most often used in business situations, such letters can be used for any number of circumstances, including asking for a raise, requesting an interview, soliciting donations and requesting a performance review.
When drafting a letter of request, it's important to include all pertinent information up front. Be concise but straightforward, including all necessary details. For example, if requesting an interview for an article or similar project, note why you chose this person, where the interview will appear, how you're proposing to conduct the interview (via email, phone call, in person and so forth), how long it might take, and when you're suggesting it take place. You're aiming for the person who receives the letter to say "yes," not to ask follow-up questions you could have addressed in your initial contact.
Though letters of request can vary widely depending on multiple factors (such as how well the writer knows the recipient and the scope of the request), they should all include the following: your full contact information, supporting documentation (if applicable), a clear and succinct explanation of your request, and a deadline for response or other action.