Picking a school based on the dating scene
I agree completely -- the dating/relationship scene at a college is vitally important to the college experience, but it's often overlooked. College guidance counselors might ask whether you want city/rural and discuss the options for majors at different schools, but I think that very few delve into the dating scene at prospective colleges.
To get some color on dating issues at colleges, check out The Insider's Guide to the Colleges, 2008: Students on Campus Tell You What You Really Want to Know. This book is great -- it features quotes from current college students describing what student life is actually like.
If you're looking at colleges for a student who is LGBT, you should absolutely order a copy of The Advocate College Guide For LGBT Students.