>>9
Don't make out of the blue then. Any gathering scene is the best time to meet new people.
Your first line to the girl should be simple, casual, making her feel comfortable in your presence. Lines like "Hey, how's the party?" "I don't think we've met.." And then develop the conversation from there. Which should be pretty safe for a first timer like yourself.
I wouldn't go as far to call her. She hasn't exactly given you permission to use her number yet.