I pull off my shirt, and invite her to my gun show.
heh...
On a more serious note, I still don't have context on this situation. Is it just a normal day on the quad with people sitting on blankets or playing Frisbee? Am I in the library minding my own business studying when she walks in. If it's -40 outside I don't even fucking bother. There's very little to no chance I pick up a girl walking texting on her phone. To me the "timing of the environment" is also just as important.
For the library example, if it's a Friday at 6pm and it's just me and her I study for a while and wait for that inevitable glance. I basically follow the same approach. I would call out something along the lines of,
"I thought I was the only one insane enough to study on a Friday evening". Then I wait for her physical and verbal response. If she laughs and agrees, great I am halfway there. If she gives a menacing look and snaps back to her book, fuck it it's not worth it. I would then ask her what she could possibly be studying, find out about her major, what year she is, what she was planning on doing once she was out of here ect.