How do you know if a boy likes you?

It all depends on the age of the boy. Typically little boys (up to 12) will be mean to you if the like you for example throwing stuff at you chasing you taking away your stuff etc. older boys will either flirt with you or (if they are a really nice guy) might jut want to be your friend and get to know you before things get more serious. And you have to remember some boys are really shy.