On campus, I've approached girls with a simple, "oh, hey", and I've noticed that they usually respond and ask me basic questions after that. I nod my head and what not, and they usually keep talking... Once they're hooked, I lead the conversation by asking them questions about themselves, and I usually say something along the lines of 'oh, you must be a science major, your glasses say it all' or something like that. They usually laugh and ask me questions. When they ask me stuff, I respond funny, half-heartedly answers (e.g., when they ask me what I want to be, I'll say something like a priest, body builder, etc.). I always examine their body language. If the girl's arms are closed or she doesn't seem interested, or she's not making an attempt to keep the conversation going, I usually say something like, see ya and they'll usually return and talk to me. I've noticed that the less interested you seem in the girl, the more likely she is to ask you for your number. However, when I've gone up to girls and hit on them directly, they usually reject me politely, is that normal? This has made me think twice about letting the girl make the first move.

EDIT: Should I even bother hitting on girls?