Does a girl know if a guy like her?
depends on.how you are to her cause you could be.in the friend zone and you like her she isn't gunna.notice
sometimes... usually its when he tells her. or someone else tells her.
sometimes. If your one of those people who express themselves, then probably yes. If not; who knows? Girls are unpredictable! :l
It depends, does this guy try to make any subtle hints or flirts?
it depends on the signs the guy gives off, and sometimes they google it and get help from pros
Usually, its obvious, but like everyone else says its hard to tell:)