I went through this process last year, and it resulted in my starting at MIT in three weeks. Here's my advice:

• Make your essay different from other people's. Admissions officers read hundreds of essays that are all nearly the same, and hate it. Make yours different enough that they get a break from the crushing boredom.

• Be candid about yourself without being clichéd. With any school essay, there's a pressure to spout BS phrases that don't really mean anything. If you can really mean everything you say, in language that's more your own than the platitudes you've been trained to write, it will show through.

• If there's any chance you can talk your parents into it, apply to more schools. As many schools as you can bear to write essays for. I applied to 8 schools and only got into 2 (my first choice and my safety). After a certain point, there's about 3 classes worth of equally qualified students applying to every school, and there's a strong element of Random Number God determining which of those get in. You need to apply everywhere you think you'll be happy and get the future you want.