The best way to write a letter of recommendation is to start out with a formal greeting, or using "To whom it may concern" if you don’t know the recipient. Follow the greeting with 2-3 sentences of praise for the person you’re recommending.
How many letters of recommendation do I need? Although it can vary, generally, you will be asked for three letters. We recommend that you send only the number of letters requested. Admissions committees do not have enough time to read extra credential.