Depends on what your goals are.
For example, if you want to hook up for sex.. then dress slutty, talk slutty and just downright act like a whore. And obviously make sure there's plenty of alcohol around.
If you want to make guy friends, then dress reasonably.. but don't expose too much. Sure you'd be making an impression, but towards the group of guys with the wrong intentions. Talk to guys, be yourself, have a sense of humour and try to be confident. Can't believe I'm agreeing with Dreamerish but I 100% agree with her post.