Use active verbs wherever possible. Make sure your transitions are smooth, not jolting. Revise as often as necessary. Proofread, proofread, proofread, and ask someone else to proof behind you. The icing is the recommendation letter.
Teachers write scores of recommendation letters, so get on the list early.
If yours is one of the first a teacher writes, it has a better chance of coming off as fresh and original. Most importantly, never miss a deadline. Keep a calendar of when each application is due. Once you've narrowed your list, try to visit as many of your top choices as you can. You can't make an informed comparison unless you've actually been there.