Feel the Heat:

Pretend to feel the heat that they left on the card when they touched it. Set the deck down and slowly feel the back of each card, turning them over and tossing them, face up, into a pile off to the side. They will be watching your eyes, so do NOT look at the pile. Instead, stare at the face down deck, and use your side vision to just glimpse the card. Pretend to be concentrating on the face down deck. The longer it takes, the more dramatic it can be. When you see the "key card" tossed off to the side, pause. Take a deep breath. Say "this is it!", and let them turn over the next card. They will be amazed.