I've read a lot of forums. Good grades are important, but extracurricular activities are more important. You need to show that you don't just volunteer, but that you are a leader. You should create some organization, invest yourself in some charity project, etc... Some get in with an incredible life story (while helping others)
Basically, you need to be a Mother Theresa
But at the end of the day...Why do you need to go to a highly prestigious school? There are plenty of schools that would make you a great potential employee, and where you can actually enjoy your young years and college life, not studying 24/7