Well, I hope you are expanding out to more than just the women attending your college, but if you live in a small college town that can be difficult.
I've always thought the "Are you single?" line might make you come off as creepy; this is why you need to have your fundamentals down pretty well. If you are good looking, have a nice fashion sense, approach with a good vibe, and are strong while doing it, asking if they are single can work.
I prefer to use this line when I'm out and about and don't have much time to chat with women, but I see one that I really find attractive. Indirect in any variety really just seems to fail completely here because she has no idea what you are about, and doesn't have time to figure it out; she's busy.
Another good thing about this line is that it is great for saving time. I'm out and about and busy as well, so I don't have time to sit there and flirt. If she's working at a desk or something I sure as hell can't wait around trying to make her like me. Asking if she's single cuts to the chase and lets you know immediately if she's interested; but it's not her answer that matters much.
No matter what answer you get you're going to keep talking to her, unless she gives a flat out no and walks away or tries to end the conversation by looking away or not saying much. Or maybe she says yes but doesn't look like she really wants to talk to you. But if she keeps talking, it doesn't really matter what her answer is because she wants to keep talking to you. That's why this line is advocated in these specific situations.
If you are smooth and not creepy about it, you can easily use this line to your advantage. Sure, it may come out a little creepy or off at first, but this is why we practice. Gotta start somewhere.