My friend's coworker, who happens to be a PUA (Pick-Up Artist), actually gave me some oddly good advice. I didn't ask for it lol, but he made a good point...
END the conversation before the awkward silence has a chance to happen. After you two have talked a little bit, just look at your watch and say "Crap! I gotta get going! See you later!" and go off wherever. The guy who told me this says that it'll make her start thinking about you after your conversation ends...