In order to do that you need to have a way to keep in touch and some outside of the table interaction doesn't hurt either.
For a while I was using some custom business cards that had my contact info on one side and something like a coupon stating "good for one free drink at the bar after the game". Needless to say they were somewhat popular, but those drinks can really eat into your convention budget fast if you aren't careful.
I needed a new "gaming card" and I'm not too ashamed to admit I totally stole the idea for mine....
Now it is no secret that my main game is HackMaster and I've spent a lot of time volunteering for Kenzer & Company "back in the day". For quite some time at the summer cons the KenzerCo D-Team had these crudely made cards that mimicked the chance & community chest cards from Monopoly.
The most common card was the "Get out of Character Story Free" card, which was intended to help extract the D-Team from the inevitable parade of PCs stories they'd be forced to listen to. What a lot of people didn't know was there was a second card they made that was "Listen to my PC Story". Over time the cards kind of disappeared, or at best there would be a half-mangled full-page sheet crammed discovered in one of the convention boxes.
My wife gets the more popular canary Community Chest version and I grabbed the orange Chance card. Printing these up at Fedex-Kinkos was dirt cheap and a great way to single yourself...definitely better than using traditional business cards.
Now I have a Frugal GM "business card", but I'm still a huge fan of the gaming card.