Watch for him showing interest in things you like and do:

For example, if you like a certain genre of music that he likes as well, he may suggest bands or artists for you to listen to. Another example, if you play sports he may ask to play against you just to show off that he’s good at something you both like and then also have a reason to give you compliments as well.

Check for signs of nervousness:

Signs of nervous laughter, sweaty palms, deep breaths, fidgeting,or possibly even looking away quickly when you notice if he is watching you are all good signs of an attraction towards you and that he is nervous about making an impression on someone he likes.

Pay attention to his friends:

If they know he’s interested in you, they might tease him subtly when you’re around, hint to you that he likes you, or even try to find out if you like him. Study their reactions to your presence – do they smile? Do they turn to him? Do they smirk in a way that suggests they know something that you don’t?

Don’t ignore him If he shows genuine interest in you, like smiles at you a lot in the hallway, work, etc., at least go out for a walk.

Look to see if he imitates you If he mimics you, he probably likes you, such as, if you move to another table, he’ll go with you. (A girl actually told me “I’ve had a guy who liked me mimic me before, so I know this is one thing”

Pay attention to teasing. If a guy teases you a lot, it might mean he likes you, but if he doesn’t tease any other girl, he probably does like you.

If he hits you or playfully punches you on your arm, this may mean he likes you. A guy may hit you but it’s just flirting he probably just wants to see your smile You may find it annoying if you’re not into him, but otherwise if you hit back then that’s a way then he can know that you like him back!