How does a Guy know that a Girls knows he likes her?

No they don't but if she's that into you then she should get rid of the guy 'cause she obviously has feelings for you. Or she should consider with whom she wants to be. But the basics will stay the same, although she should/might be more careful about her displays or actions towards you. Perhaps she'll do it a bit more down toned than if she were unattached, at least when around other people.

Mostly she'll be talking to you every time possible. Sometimes though we don't want to look needy or desperate so maybe we'll give you your space, but trust me when a girl likes a guy she will be desperately trying to see him or talk to him whenever possible.

She'll also laugh at your jokes no matter how stupid they may be, she'll be genuinely interested in you, ask things like how your day went, if you have a problem, she'll push you to tell her so she can help you, bottom line, she'll want to know everything about you and it's great for us if you tell us your problems so we feel like we are you're support, just don't over do it and be whiny about everything..

We are nurturers by nature so we will try to fix your world however possible, or think we are doing so, even though we probably aren't. We might ask about your feelings, dreams and goals. If the girl isn't too shy she will try to touch you, your arm, hand and mostly your abs or chest if it isn't of course in a very obvious and desperate way. She will lock eyes with you a lot and there will be an uneraseable smile in her face whenever she's around you or talks with you.

When she's with friends she might be talking to one (who will probably be annoyed that she's listening about you yet once more lol) and might be looking over at you. And a definite clue is if you talk to other girls in a flirting way she might get jealous, she won't take her eyes off the two of you to see how you both are relating.. Hope it helps. =)

Just ask her out if you like her, man. It's a 50/50 or more ;)

She leans toward you when you talk, you look in each others eyes a little longer and you start to move a little closer to each other as chemistry builds in the conversation. She might brush up against you often when she passes by. She may touch your arm, hand or shoulder during conversation or beginning a conversation. She could give you a smile, not like I'm at the circus, YAY! smile but a hmmm, I wonder what he thinks of me smile. You know, that curious magazine cover smile. And she finds a way to be around you. Maybe not all the time, but enough to keep you thinking about her, and often(I think). (I asked the same ?, so I'm sharing what I got). But women are going to be a lot more helpful with their responses. I'm just trying to give some examples to help.