A lot of girls will cross their legs around a guy they like and of course touch their hair but they also will keep eye contact when they talk to you and possibly will even blush but quickly look away so you won't notice.
Many girls, don't just talk to any guys especially a lot, she got to have some kind of feeling for you. She got to like you and probably want to see if there is a future with you two. The girl who talks to that same guy a lot mean she likes him and if she flirts w you back ,that a positive sign.
Beware of the girls that just flirt for fun and they just practice flirting for the next guys. Usually these girls doesn't care to talk to you a lot and go on with their own life. They would not call you at all and but they still pick up your phone calls because they are lonely.
I so know how you feel. my guy friend and I flirt a lot and everyone says its obvious that he likes me but it isn't obvious to me. sorry I realize that wasn't very helpful, just thought I'd let you know you aren't the only one out there lol. best of luck though.
Watch for body language. When she's looking at you (and you're not in bright sunlight) do her pupils get pretty big? Does she smile with her eyes? Does she adjust her hair or run her hands through it a lot?. Well never mind all that. You like her obviously ,so ask her out. If she says no, you get to stop wondering. And if she does like you, she'll say yes. But don't make the first date a movie. You won't get to talk much.