Ok, here's how I recommend you go about this. I'm guessing you're a junior. Find about 6 or 7 schools that you're really interested in, do some research on them, talk to students etc.
I HIGHLY recommend doing Unifieds your SENIOR year. If the colleges you are interested in are all going to be in one city, call those colleges and talk to them about unifieds and schedule appointments. This way, you'll be in one city for all your auditions instead of traveling all over the place.
http://www.unifiedauditions.com/ On that site it gives a list of every college that will be in the major cities auditioning all at once. LA, Chicago, NY, Boston etc.
Find pieces that fit the requirements and that work really well with your voice etc.
You'll have to have a bunch of different pieces ready depending on which colleges you apply to. Some require shakespeare, some don't, some want 1 song, some want 2.