The Best On Campus Housing
You can put it simply: the best on campus housing is a single room with no roommate and a private bathroom. It would also be great to win the lottery---i.e. both are not likely to happen. If you're an incoming freshman, you are basically the low man or woman on the totem pole, so you won't be able to choose where you live.
As you move up the ranks in the college, you'll most likely be able to get better living quarters. For instance, juniors and seniors are able to have single rooms. Unless your freshman roommate leaves school, you're most likely going to be living side by side with another person.
This is not necessarily a bad thing. Most students will know very few people on campus: perhaps a few people who went to the same high school. Often, new students will know nobody at all, so it can be very comforting to have a roommate. It's not always recommended to try and get out of living with a roommate the first year of college.
Ordinarily, you'll fill out a questionnaire regarding your interests---music, sports, books, etc.---and your roommate will be chosen accordingly. Often, people on entire floors will be chosen according to these initial questionnaires. If you absolutely do not get along with your roommate, it is possible to request a change. Students have been known to trade roommates as well.
Incoming students often have no real choice of the dorm they are assigned. Certain dorms on any campus are nicer than others. One dorm might have cinderblock walls whereas another will be in an older, more attractive building. It is possibly to request certain dormitories, but the choice might not always swing your way--it's the luck of the draw.
Students live in off-campus housing as well. Depending on the location of the college or university, students will live in an apartment, shared apartment, or room in a house. Again, this is not totally recommended for incoming freshman, as it can be alienating to live far off of campus. It may make it harder to make friends. However, in some situations it can actually be cheaper to live in an off-campus apartment or rooming house.
What it may come down to is this: you have to get the lay of the land before choosing the ideal living situation. Unless you know a school intimately before moving in, a student will get a sense of the best dorms on campus or the most convenient neighborhoods off campus. For this reason, it's very important for a student to have a thorough tour of the campus before applying. This way he or she will be able to request a certain type of housing.
Often, students will not be able to make a fully informed decision about housing until sophomore year. As a sophomore, a student will be able to choose a roommate, explore off-campus housing options, and choose the best dorm on campus. If they're lucky, students will be able to make a change in the second semester of the first year.