If you have an idea of what you want to study, then find
Rugg's Recommendations on the Colleges by Frederick Rugg. Your local library or your college center at your high school should have the book if you don't want to purchase it. Once you know the schools, look on the websites of the schools to view the admissions requirements/ current freshman stats/ school size/ cost of attendance (tuition, r/b, expenses) etc. If you are undecided as to a major, then look at size, geographic distance, academic reputation. Your PSAT score will provide a score that can give you an idea of target schools. If you have low 500s in everything, Harvard is relatively unrealistic in terms of admission and you may not want to waste your time in exploring that option. Conversely, the student with 700s in everything may do better looking at Tier 1 schools.
Since you are in hs, I'm sure you know that the SAT changed significantly for the high school class of 2006. It is now 4 hours long and it is 3 sections of critical reading, critical writing (includes a timed essay), and math. Analogies were dropped. Math concepts are through an Algebra II level. SATs used to be 2 sections and the max score was 1600. Now a perfect score is 2400.
The college application process is daunting to say the least. I can go on and on about this. I'm happy to answer any questions. Start visiting colleges during your Spring Break this year and arrange overnight stays in the dorms. Some college admissions only arrange overnights for hs srs. The new buzzword is "fit". This is something that really can only be experienced by visiting the schools.
There are a lot of great forums that are devoted to the college application process including merit and need-based aid. I found them AFTER my D had been accepted to school but I stay on the boards for my S's process. My favorite is
http://talk.collegeconfidential.com.
www.admissionsadvice.com is also helpful but it doesn't get the quantity of user traffic.