I'm glad I don't have that problem. According to my kids facebook page he is already at Stanford. 
But I agree with James G. First two questions are how far and what size? Then you can go from there.
What's being considered when evaluating school size? I didn't attend college but I'm encouraging my son to.
Some Colleges are in what are called College towns...these are towns that are only truly alive when the college is in session. They usually have 2-3 pizza places that have a $5 pizza, 3-4 bars (way more than an average town would need), 2-3 used book stores, 2-3 tattoo parlors, and other shops that are geared towards college students and not a normal town. Those colleges usually have about 3-8 thousand students, the dorms are on one side of campus clustered together near the real cafeteria, and the furthest class is 15 minutes walking distance, with some sort of college hub in the middle of the class buildings, such as a student union building that has food and maybe a book store.
There are what some people call urban schools which may utilize class buildings miles from each other and set in the middle of a metropolis, such as Georgia Tech is in the heart of Atlanta. The dorms are far away from all classes and whether school is in session or not the neighborhood thrives.
My best advice would be to ask your son what he pictures college life to be. Is he hanging out in the dorms with his buddies and then walking his girlfriend to class then grabbing a bite at the cafeteria before hitting the gym? Does he see himself still living at home? Does he see himself living off campus immediately (My school had a provision that I had to live in the dorms for at least 1 year)? Does he have a roommate in this vision? When he thinks of "College" ask him to paint the picture for you that he sees in his head, that should help narrow down things a LOT!