Once you have these basics, focus on your needs. For us, it was things like availability of good Asian food off campus, team for his sport where he would actually get a chance to compete (ie, good but not only Olympians), depth of involvement in and mentoring for coding/math/hacking competitions, availability of world-class research in 3 specific areas he wants to focus on eventually, availability of coterminal BS/MS degrees, etc. The more specific you can get, the better you can drill down to good options, especially if you are looking at some giant schools.