You could make fun of what she is wearing. One of my friends passed by a girl he didnt know and said "Psshh, nice earrings." A back-handed compliment.
I might say, " I'm going to hit on you, are you single?
If yes... Well, lets get together/hang out sometime. You have email? (If yes, great, tell her to write it down, if no, "well write down your phone # and then we can get together, I'll set up email for you, and then we'll have a party to welcome you to the 21st century."
If she is not single, "Haha, well, that is too bad for you, infact, I feel so sorry for you that I'm going to give you my number." (If you have a card, great, if not, have a pen ready and paper.)