This is simple. As a girl, almost any line works. Select your intended victim and just say what pops into your head. My specialty is bar lines, but then, I'm an alcoholic. Be bold, be daring, and above all, be confident.
Some lines have become so bad, they're good again.
You could try bumping into somebody and demanding that he buy you a new drink. This approach might be too much for some, but borderline rudeness has always worked wonders for me. You can meet people on campus, at bookstores, coffee shops, at Narcotics Anonymous meetings, on the street, at your dealer's house, through a friend, better yet, through the guys you're dating. Once you've infiltrated their little club, by all means, take advantage. The important thing is to recognize that opportunities are everywhere, waiting to be grabbed or otherwise fondled.