If you want to know whether a guy likes your or not, the trick is to understand how he usually acts when you're not around, and whether that changes when he's with you.
That's the best way I think.
Because all guys are different, some will get really flirty, some will be distant and ignore you, some will get hyper and shy.. It's all about whether you have made some sort of impact on the way he behaves.
How can you test this?
Get one of your friends to go over and talk to him. Make sure it's someone he feels comfortable talking to.
Then, all of a sudden go and join the conversation.
What does he do? Does he react differently? Ask your friend afterwards, although you should also be able to pick up on a change in him