I Stumbled Upon This Trick by Accident
Say you approach a girl and start chatting her up. Her name is Lindsy.
After you talk to Lindsy for at least 30 seconds or so (could be longer though), say something along the lines of:
"Most girls I've known named Lindsy aren't very nice. I'm glad you seem nice. You seem like an exception."
Say this even if she doesn't seem very nice yet (unless she's a total b*tch). She'll try to redeem the "Lindsy name" by making more of an effort to be nice to you.
I recently stumbled across this trick by accident. I was talking to a girl named Lindsy in one of my classes, who was kind of ignoring me and not making any effort in the convo.
About a minute into the convo I asked for her name -- Lindsy. I made the comment that most girls named Lindsy aren't nice because in my experience this has been true. But I called her nice just to compliment her, hoping to make her a bit more friendly.
It obviously worked because ever since that she's been MUCH more friendly. She also brings up that comment often as if she's trying to prove how nice she is!