There are a couple of different ways that you can tell if a guy likes you. You can tell if they flirt with you a lot or like to hang out a lot. Usually men like to keep in touch if they like you. They may kiss you to let you know they like you. If your friend is always asking where you are then then there is a good chance he likes you.
You can tell if a guy likes you because he will start to become interested in the same things you are, and you will probably see him talkin to your friends. And espesialy if this said boy who has never talked to you is now all the sudden striking up conversations with you.
If a guy like you he may or may not be obvious about it. He would smile at you once in a while and maybe even pick on you because he is trying to not show it as much. But then these the guy that always wants to be around you all the time constantly starts at you always wants to sit by you.