Greet her and say what's up, ask for her name(even if you already know her name, that way she doesn't think you're creepy), no matter what the name is tell her "Oh that's a nice name" and then tell her you think she's cute and then make up the rest of the conversation along the way. Or if you're shy say something like "I'm in a rush can I get your number so I can talk to you later"