how do you know a guy likes you?

Depends on the type of guy

With shy guys you can tell with body language

With the other "type" of guy theyll come up to you straight up and say "I like you, will you go out with me" etc etc

It also depends on if the guy wants a serious relationship or not

cuz they could always like you...but never say

On the other hand they could say they like you but....not really be serious about it

anyway please make your question less general and i tried to help as best as i could

Good Luck

and it seems by mentioning "this guy" you seem to like him too...good luck to the pair of you ;)

Just Check Out His Body Language Around You, For Instance If Your In A Deep Conversation And His Feet Are Pointed Toward You, He's Interested. Also If He Looks At You And Looks Away After He Speaks, Or Is Constantly Looking Back And Forth At You, He May Be Interested. You Can Tell A Lot From A Persons Body Language. Good Luck:) Also If His Hand Or Finger Is In Front Of His Mouth Alot That Can Be A Sign That He Is Shy. :)

when he comes up to you and asks if you want to go see a movie with him.

start flirting with them and see what they do back....