You may know if the guy likes you when texting if he says he does.
when he says he likes you.
iam in love with this guy but i do not know if he likes me or some other girl
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
You know when a guy likes you when he asks you out and shows a shine to 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.