Using business email format, ask a former or current supervisor or professor for a recommendation letter. Because you need to persuade your audience to write for you, you should follow the INDIRECT style, which means withholding your purpose in writing until the middle of the message.

A successful request for a recommendation will follow this outline:

First paragraph mentions how the reader is acquainted with you $($e$.$g$.$ what classes you took with the professor during what semesters$/$years$)$ and what you learned from the reader$/$why your experience with this reader is important to you

Next paragraph$($s$)$ ask for the recommendation, and supplies details that will make writing the letter easy. Explain exactly what you want to be recommended for $($acceptance to a particular school, an internship at a particular place, etc..$).$ Remind the reader of the specifics of projects you did, papers you wrote and$/$or accomplishments that the reader helped you achieve. Don't forget that the reader does not know what what is most appropriate to include in the letter because the reader is less familiar with what you want to be recommended for than you are. This part of your message goes a long way to reducing resistance by making the recommendation easy to write. In fact, you should not be shy about supplying enough detail that you are practically "writing the recommendation" for the reader. Your reader will thank you.

Next paragraph$($s$)$ discuss the influence that the reader has had on your success, and the value that the reader's recommendation would have to your future $($this is the "incentive" for the reader to write for you$--$that s$/$he can influence the course of your life and thereby feel that they are valued and important$)$

Last paragraph should give the logistical information. Tell where the letter should be sent $($to what physical or email address$)$ to whom and by when it is needed. Avoid having recommendations sent from the recommender to you, as decision$-$makers often find recommendations sent directly from the recommender to them to be the most persuasive.