Sometimes it's difficult to tell if a "joker" type guy has genuine feelings for you, especially if he tends to be a flirt. But something to watch for is seriousness. If he looks you in the eyes and is able to seriously talk to you about something meaningful (especially if it's about you or a potential relationship between you), it may be a good sign that he is interested in you.
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.
http://www.wikihow.com/Know-if-a-Guy-Likes-You
Not sure how you expect someone to magically know something.
It is ok to like a guy after you know he likes you. That is perfectly normal and a part of life.
You ask the guy.
don't
When he has a penis.
his eyes will open wider if he likes it
If he says i like you
Trust me. You will know.