Guys are tricky. Sometimes they like you for real and sometimes they just act like that because they are close to you now. If he glances at you every minute, or tries to get you alone with him. Or if he pulls out chairs and opens doors for you. He could text you saying how much he could trust you or how pretty you looked at school or wherever he saw you. He may also smile at you a lot and try to next to you. He may be the shyest guy around but he'll talk to you. The best way to know is that he starts falling over things then he asks you out
Be honest most guys are simple and like honesty. Tell them the blunt truth and all will go well. That way you regret nothing even if it does not turn out well.
A guy might talk to a girl or this guy may keep looking into a girls eyes. This guy may also do stupid things to get a girl to notice him. If this guy is shyhe will just take a few glances at a girl, and if a girl sees him doing that, he won't look at you again for a while.
He may or may not be obvious in showing it. Some guys like to play the cool dudes. Then others are overbearing. He'll smile a lot at you, and you will catch him looking at you often. He will make attempts to be next to you and compliment you too.
Don't forget that he may try to touch your arm or talk to you more than your other friends.
A big thing too is when you are in a conversation with a group of people, even if it's just you, him, and someone else, and he's talking, even if what he's saying is directed at everyone, he'll say most of it looking at you.
When he doesn't avoid you, he talks with you softly and listens to what ever you say.
This is just me but when I was in the room with the girl I liked I became A LOT clumsier. I fell over chairs, I even ran into a pencil sharpener once. So yes if he's doing that, it might be he's into you, or he's just a klutz.
If he makes an effort to talk to you. Guys are nice to girls they like. Ones they don't they will never look at, never talk to.
Give him your number and see if he texts/calls.
You can usually tell by the way he texts/or calls if he wants to be mates or more!
I am a guy and I can tell you that to a guy his time is very important, especially if he is a busy guy. If he is willing to spend large amounts of time with just you, (ie. tutoring or studying), then he probably likes you. Many times if you ask him to come over and help you study he will do it if he likes you, but if he does not he may refuse or be 'busy'. So go ahead and ask him out, if he is shy he may never build up the courage to do it. If he is very smart or math oriented, like me, he will have a hard time convincing himself that he has a chance with you. You must either give him some pretty darn obvious hints or ask him yourself. Believe me he will LOVE it if you ask him.