How do you tell if your friend has a crush on you?

You WILL know! If you are a girl the boy might not tell you BUT through his actions you will feel something else then what you usually feel with other boys. It will become VERY obvious!

A:

probably he'll/she'll glance at you more often, or you might catch him looking at you(if he's/she's shy, he'll probably look away, if he/she had the guts then he will smile at you--it depends on the person,)

he would also tease you or sit next to you(those common things a guy would do if he's into you)

(edit from another person)

If the person you like is a guy, he might be unusually quiet around you. Not silent, just talk more softly.

Irregardless, one thing that I have heard works is this...

Stand close to them, closer than would be comfortable. If they notice, but don't move away, then there is a good chance they like you. (Personal barriers are different for someone you want to be close to, and they will allow you to be near them well beyond the usual comfort zone)