I don’t think you should think so much about flirting, and instead, try your best to get closer to him in a genuine way. Look for common interests, reasons to be near him, etc. If you like someone, flirting comes naturally, and before you know what you’re doing, you’re acting dorkish and silly and giggly and you’re off and running. You have to establish a bit of a connection first, though. I don’t know about others, but I think flirting comes off better if it’s fairly subtle (but not too) and if it really is genuine (as in, not reminiscent of random pick-up lines scattered throughout a conversation). If you spend so much time thinking about the fact that you’re trying to flirt, well, it will probably blow up in your face. People don’t do as well with conversation if they’re constantly examining how they’re coming across. I think it hinders progress. Of course, I’m probably the wrong person to talk to, since I rarely flirt with people and find it a bit silly.
How to get his attention? Do the little things. Smile, and laugh, and show that you’re light-hearted and fun-loving. Keep unwavering eye contact for a few moments when your eyes first meet (a recent study shows that males are more attracted to females if they keep eye contact instead of looking away–it shows that they’re interested). Be as confident as you can despite the fact that your heart may be pounding in your chest. And make it clear that you do like him. You don’t have to come right out and say it (that could very easily scare him–-professing feelings almost always seems to scare them), but if you show it, and don’t play any head games or pretend to be more interested in somebody else to evoke jealousy, that should help.
It’s always tricky, and as Carnun said, the way you act really depends on the person you’re around. It isn’t hard to see what somebody likes and doesn’t like once you start spending time with them, so use that information to help you refine your flirting. Just start out slow, feel him out, and continue on from there. If it appears as though he’s not interested despite your best attempts to make him interested, take that as a sign that he may not be into you.
There’s this new book out called He’s Just Not That Into You. I haven’t read it, but it sounds pretty interesting and helpful for those confused about relationships. If it seems like nothing’s working, don’t compromise yourself and continue if you’re getting nothing in return. Tell yourself, He doesn’t know what he’s missing and gracefully bow out. No point pining away for some dope who can’t see you standing right in front of him.
Long post! I’m sure others will have some interesting things to share that may help you out. Good luck.