I am a student at the University of Pennsylvania, and I would say a few things:
1) Extra-curriculars, especially unique ones. It sets you apart. You don't want to look like you're trying to rack up extra-curriculars either, because colleges know the kids who are doing it just to look good. Also- don't sign up for the trip before senior year last minute that goes to Guatemala or something and make it the highlight of your application- the college will know you're trying to fit something in.
2) Connections - do you know ANYONE there?
3) The essay- go buy this book, it's by the Harvard press or something, and it's "100 College Essays" or something, all of which got the people in. It's just a list of really good ones and where the people got in to school, and it also has commentary from the school admissions officers on their likes and dislikes of each one.
4) You really do need to do well on your SAT. You can't get around that.
5) Take a summer course at a local college in your town. It looks good because you're eager to learn.
Good luck! It's TOTALLY worth it. I love Penn - huuuuge party school, believe it or not. I applied to all the Ivy's and I'm so glad I chose Penn. I started a fashion magazine there, too. You should apply!
