The best way to learn is to write one first (whatever you think is the best way to do it) and then ask your friend to edit it. Read online (the links below posted by Krishna are a good start). In general, when you write: be authentic and make it original. Send what you have here in this thread and we could provide more suggestions. If you would rather want 1-1 help, send us a message in https://www.facebook.com/collegesodhpuch/ and we can provide some feedback.