Sample request letters are available at websites such as SampleLettersWorld.com and WriteExpress.com, and you can use them as a guide to writing effective letters requesting that something be done. Examples of request letters are those asking for an interview, information, and the help of a third party, according to WriteExpress.
A request letter can also be used to ask permission to use a copyrighted material. A sample of this type of request letter is available at JaneFriedman.com and WUSTL.edu.
When writing a request letter, write clearly and concisely, and go straight to the point, recommends Chron.com. Use the opening paragraph to introduce yourself and your intention. Use the next paragraph to provide information about your request, as well as any details that may help the recipient meet your request faster. In your closing statement, thank the recipient for his time and consideration, and provide your contact information.