How do girls secretly flirt with guys?

Well what I do is look deeply into his eyes.

Or I try to make him laugh.

Or laugh a little cute laugh to make him giggle.

Lol.

when we first start to like a guy, we don't want to let them know because we aren't sure if they like us back. Usually we will just glance at the guy to see if he is looking at us. We may also try to make a little eye contact and gauge the guys reaction. We try to convince ourselves that the guy likes us back by taking every little thing as a sign. For example, if a guy we like is really nice to us, we take it as a sign that he likes us back even though in the back of our minds we know that it really means absolutely nothing. So bottom line is that the girl will be looking for signs that you like her back before she puts herself out there. Once she thinks you like her back, she will be more flirtatious and make more eye contact.

A lot of times.girls don't want guys to know that they like them (like you said scared of rejection, etc.) So as females, we find subtle ways to let you know. However, a lot of times we think we are being soooo obvious, and that guys are just not are picking up on the signals. So if your asking about a specific thing a girl has done, you'll have to divulge some more info. But girls try to "secretly" flirt by glancing your way often, smiling, giggling, finding a reason to tell you something, or touch in some way (like fixing your collar etc.), I mean the list goes on and on. But, like I said, a lot of times we think we are putting ourselves out there, and guys are not reciprocating the signals. Hope this helps a bit :)