Ho do you know if a guy likes you?

Not very easy to answer that one you're to vague, what is he doing?

His pants start looking like a tent.
His emotions are over the top.

Long list of signs:
* If he wants to talk to you all the time,
* If he starts acting nicer when you’re around him,
* If he says yes to all the things you ask him to do,
* If he treats you differently to other girls,
* If he looks at you a lot every time you smile or laugh.
* If he acts immature around you, like poking, teasing or playful flirting,
* If he seems to always want to hang out with you,
* If he gets closer with a body part, or if he tries to touch you,
* If you catch him peeking at you and he smiles,
* If he tries to make you laugh, or if he tries to copy you,
* If he walks up to you out of the blue and hugs you,
* If he tries to keep you in view for as long as possible, or tends to look around and stop when he finds you,
* If he subtly looks at you but makes it look like he is looking at the girl next to him,
* If he goes out of his way to talk to you, for example if he goes to the other side of the school to talk to you because he knows you have a class there.
* If you block him on instant messenger and stop talking to him, and he finds a way to talk to you,
* If he invites you to his birthday party or any kind of party,
* If you flirt with a friend of his when he can see, and he looks jealous or automatically flirts back,
* If he talks to you and wants to know how you’re doing,
* If he is nicer or tries to talk to your friends.
* If he asks about you to your friends when you’re not around
* If he asks you to dance with him at the dance.

You know when a guys likes you when his body language shows it, when you are around he smiles if he asks for your number..Teases you a little bit, complements you and the most important of all if you like him and he can feel you like him then it gets kinda obvious that he likes you.

Being a guy, I can tell you that when I like a girl, I usually spend a lot of time just staring at her (like in class) and turning away when she looks back, then be extra friendly to her, make her laugh, compliment her, just basically make her feel comfortable around me, I might invite her and friends to a movie and put my arm around her, or spend the entire day hugging her...
Basically anything that is affectionate probably means that he's attracted to you, guys aren't really that complicated...XD

If he begins to flirt, stare into your eyes, or drop hints like one that a guy told me, "I like this girl who has long nose, kindof like your" if a guy does this than he probably like you.