MY COMMENTS:

First of all, I admire the hell out of you, because you did
SOMETHING instead of NOTHING. Nice.

Now, as for what to do in a situation like that one...

I have a friend that does something interesting. He'll call
the waiter over, and say "Can you deliver this napkin to
that girl over there? But don't tell her who it's from." Then,
he'll draw a tic tac toe game, and put an X in one of the
squares. (Always tip the waiter a dollar!)

The napkin almost always comes back, and the game is on...

It's fun, mysterious, and the girl always wants to know
who's playing with her.

I've used this before, and it's great fun.

At some point, depending on whether you're winning or losing,
you can come over to her table and say something like "Well,
I had to meet my worthy opponent" or "I hope you talk better
than you play" etc.

Also, if a woman gets up and is about to leave, that's a
GREAT time to go get her info!!!

Just walk up and say "Hi, I was going to come talk to you
earlier but I got busy... what's your name? Do you have
email?" Easy. And it's so natural to ask, since she's
obviously on her way out...