Just say "Come on I'm interested" or something else which urges them on. Then don't say a single word:vacuum it. (Credit:
Juggler) You have to use the awkward silence to force them to make the effort. Once they do say something cool respond with a strong IOI, then either IOD or continue on depending on their response (watch body language for this one, your calibration has to be pretty good to know which way to go here.)