Aw, bless your heart! You've already been given excellent information to consider. Just adding some more.

In direct answer to your questions:
-I've been told NOT to get a kitten as my first cat. Instead, I should get a cat that is about a year old? Is that true?
Kittens, like babies, are a LOT of work. They're time-consuming. And they are best adopted in pairs, because in the end, they're less work on you as they have each other to play with. Kittens are both a delight and a nightmare. You can always add a pair of kittens if you adopt a one or two year old now, and once you've graduated college, at four or five, your existing cat won't be a Senior, and a couple of kittens might drive him or her nuts, but won't put him or her over the edge.
-I've read that cats and down comforters don't get along... is this true? Umm... depends upon the cat. For us, it's not true. Cats love playing blanket wars with any comforter or blanket, and if you don't want your legs, hands, or feet attacked during the night, it's best not to play that game (though really, it's so darn cute it's kind of irresistable).
-with dogs, breed is very important in terms of personality and behavior... is that true with cats too? If so, are there any breeds I should avoid? No. Different breeds do have different personalities... but most cats are just "domestic short hair" or "domestic long hair," and it's nearly impossible to tell what's in them.
-do any breeds shed less than others? (the less, the better) Not to my knowledge (unless you get a hairless cat). This, in my experience, really depends upon the cat. We have one cat that seems not to shed much at all - another, you touch her, and you have a handful of hair.
-When I go to a rescue or shelter, what should I be looking out for when picking out a cat? (in terms of behavior, disease, etc.) Given you're going to have a number of roommates, you're in college and there'll probably be a lot of people in and out, potentially lots of noise... I would definitely look for a really social cat that loves people.

I get Ducman's point about kittens... but with older cats, the people that have fostered them or that shelter them typically have a real good feel for their personalities. With kittens... while you can sometimes get some kind of feel for what their personalities are, it's the difference between adopting a 3-year old and a 12 year-old or a 20-year old (not in terms of maturity, but in terms of knowing what kind of personality you're getting). And I'm pretty sure you'd like to have a cat that doesn't mind people and is outgoing. You don't want a scaredy cat that's going to hide under your bed, or want to when things get a little noisy or busy.
-Also, are there any major differences between males and females? (after being spayed/neutered). Well, just like with people, there are generalities, and there are plenty of exceptions.

In my experience, and in seeing the cats of TCS, I'm going to have to say that generally males are more outgoing, more social, and more accepting of new cats if you decide to enlarge the family. Females tend to have a jealous streak and often are more pissy with other cats. That said... there are lots and lots of females that are really social and love other cats. And our Sheldon has a jealous streak a mile long.

In the end, you'll see what everyone means about the cat picking you, and I'm not sure you'll have much choice whether the cat that adopts you is a male or female.

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Lokilove brings up really good points about the cost of a cat. And some shelters and foster networks do ensure the cats they adopt out are healthy, and have been treated for parasites, etc. Others say they do, and then people turn up here wondering how to treat giardia, or coccidia. The realities are that there are so many cats in need of homes, some shelters/foster networks are really busy, often at max capacity, and you just cannot guarantee the health of an animal. What I recommend you do is find the vet you want to use, and whether the cat is "guaranteed" to be healthy or not, you take kitty to the vet, and unless you have the schedule of when what parasite medication was given to the cat you adopt, you assume kitty has internal parasites that need to be treated.
I don't know what your financial situation is, and you obviously don't need to tell us. But some food for thought.... My husband and I rescue, and things got tight for us financially. What we do is make payments whenever we can to the vet - we generally build up a credit balance. You might want to discuss this kind of arrangement with a vet. That way for any emergencies, the money's already there if you need it.

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Pets are a big responsibility. Are you prepared to play nurse if necessary? To clean up pee, poop, and vomit, if need be? Is it going to drive you insane if your cat chews wires, is fascinated with gravity (dumps drinks, for instance - I've already had one laptop ruined and another close call), or scratches the furniture? You going to be able to clip claws?
I am NOT trying to talk you out of adopting a kitty! Just making sure you're sure you're ready. Because as Lokilove points out... pets are for life. When you're a parent, you don't adopt out a child when life changes up on you.....
Please keep us posted! And if/when you do adopt a kitty, remember, we love pictures!
Good luck - and have fun!