Kendall
A lot of choosing the right school comes just from intuition. You shouldn't pick a college based on the location or scenery, nor should you base all of your opinions on what a tour guide tells you about the social life (half the time they will lie if parents are around anyway). Look at what different departments have to offer that relates to you, and try to talk to current students to get a feel for the social situation.
Kate
Don't choose a college simply because it is a big-name university. Refer to lists other than U.S. News and World Report's rankings -- books like Colleges That Change Lives or the alternative rankings from Forbes (which include many schools from U.S. News but uses a different ranking system and provides additional information). There are hundreds of lesser-known colleges that provide highly qualified and extremely caring faculty and staff, countless opportunities for personal and professional growth, and the supportive community that students need when they leave home for the first time. The presence of peers with the same drives is vital to a truly satisfying academic and social experience.
Think about what you're seeking on the way to your degree; if your only goal is to graduate and you don't think about the academic work and opportunities along the way, you will get restless and probably won't graduate at all. Seek out the opportunities available besides the classes in your fields of interest; colleges offer opportunities beyond your wildest dreams. Get involved in a meaningful student organization to make like-minded friends and add still more richness to your life.
Veronica
Take the time to visit colleges. Don't let money stop you from seeing the campis; the visiting experience can tell you a lot about the school and is often different from how the school appears on paper. Once enrolled, get involved with everything that you are interested in; you will regret it later if you don't. Don't be afraid of people who are different from you, they may end up being your best friends. Be open to things that you never thought you'd like (ie sororites/fraternities) because some things turn out to be different than you thought. Don't wait to start something. Don't wait until your senior year to start thinking about graduation and the after. Most importantly, have fun! This is the best time of your life and you'll never get it back, so enjoy it while you can. Make memories that when you look back, you'll smile and think how great this time in your life was. Live it up, baby!