I am researching colleges and I would like to know what questions I need to answer, e.g. cost of living, tuition, proximity, library size, housing, etc.
This totally depends on you. For example, cost of living was not something that mattered to me, but religious accommodations were. Some things that may be important to you (other than, of course, whether or not you could get in):
Climate
Required to live on campus? Guaranteed dorm spot?
Allowed to have a car?
Clubs and extracurriculars
Sports
School spirit
Career services / job placement
Dining options
Surrounding area
Nightlife
Greek life
Diversity
Gender ratio
Course sequence for your major
Class options
Class registration / availability
Professors
Research opportunities
Internship opportunities
Retention rate
Graduation rate
Number of students
Average class size
Student:teacher ratio
Calendar plan (eg semester, 4-1-4, etc)
Political climate
Setting (city vs suburbs)
Types of housing available
Core curriculum and requirements