To me, I can always tell if a teenage guys likes you when he flirts a lot, flips his hair, and stretches. Hope this helps
If he smiles at you a lot and is sweeter to you than before then he likes you.
youll know
Flirt, that's the best, hang out or if your really not shy, ask him out.
when he says he likes you.
http://www.wikihow.com/Know-if-a-Guy-Likes-You
If a guy likes you but you don't know him he may look at you or walk by you whenever possible.
go to this website http://www.wikihow.com/Know-if-a-Guy-Likes-You
if a guy likes you he will: smile at you, stare, talk/hang out a lot, he will try to get to know you. hope this helps.
You will know when a guy likes you when he always wants to be with you puts his arm around you or if he says anything about your clothes
Not sure how you expect someone to magically know something.
The only way to know 100% if a guy likes you is to ask him. If he doesn't show it, there is no way to know.
You ask the guy.