Unlike most other universities in the UK, Oxford and Cambridge are run under a collegiate system; that is, the universities comprise many semi-autonomous colleges that function as smaller academic, living and social communities. While the university determines course content, sets examinations and awards degrees, small-group teaching is organised by individual colleges.
Accommodation: For which years of study does the college offer accommodation? Would you prefer to stay in college for all your university years, or would you like to experience off-campus housing as well?
Location: How close is the college to places that you are likely to have to access frequently (e.g. university centre, sporting facilities, faculty buildings)?
Size: How many students are part of the college? Would you prefer a small, medium or large college community?
Environment and ambience:
Course offerings: Does the college offer the course that you are applying for?
Typical offer conditions: How strict are the typical offer conditions from that college?
Academic ranking: How competitive is the college academically? Would you prefer a more academically-driven environment?
Faculty staff: Since your tutors will be from the college, are there faculty members with research interests that align particularly well with your own, and who you would really like to be taught by?
Wealth: How large is the college's endowment? How does this affect the resources offered by the college, from the quality of accommodation, to the generosity of grants and scholarships?
Extracurricular and social scene: Does the college offer the extracurriculars (e.g. clubs, sports teams) that you hope to participate in? Is the college known particularly for certain extracurriculars, and do they align with your interests? Note that some extracurriculars are offered uni-wide, so you could still participate in them if your college does not include it.