How to respond to friend request?

Hi guys. Since this is my first post here, I figured I'd mention that I lurk around different PUA Forums quite a bit, I know the general PUA concepts, have some experience getting number and kiss closes at bars (which I've gotten lazy with recently as well and reverted to AFC stage), but I'm completely clueless in online game.

I have a facebook profile, but I rarely use it (I go on about once a month, haven't updated the profile in years, and the only pictures are ones that my friends tag me in). One thing that seems to happen quite a bit to me, however, is I get friend requests from cute girls who have either gone to same school as me, born in same city, or share a mutual friend. I'm not talking about those fake profiles that put up a picture of some model, put up generic garbage, and start friending everyone to spam them with some advertisement. The profiles are unique, have genuine wall posts from friends about current events, and I don't really get any spam once I accept the request.

Anyway, what I usually end up doing is accept the request, then send some boring "Hi, noticed we have _____ in common, you still live in the area?" and usually end up getting no reply, occasionally I get a reply and we get some boring small talk until the conversation fizzles and dies. Obviously my lame opener isn't working, I was hoping you guys could give me some suggestions. I was thinking of teasing them about sending a friend request to a stranger, but don't want to come off rude (negging is a lot easier in person). This doesn't seem to fall into the same category as other threads I see here since in this case it's the girl who initiates contact.

Thanks