You already know one key to winning my heart and charming me into editing your papers: say please and thank you. But there’s something else you can include in your email, something that will help me do a better job of helping you:
The more I know about what your teacher expects, or what the college admissions officers want to see, the more likely it is that I’ll provide meaningful feedback. Want me to take a look at your paper? Send it to email@example.com. Due to time constraints, I can’t get to everyone; also, note that I may quote from your paper (without using your name) in a post.