I think siege's description on how to do it is almost exactly as the one mentioned in RRTCM and the one I use. The key is to only move your dealing hand. Furthermore, the position of the pinky is important for controlling a card (don't need to say more, do I?). It wasn't until I read RRTCM that I realized the importance of the pinky. What I do when practicing the overhand shuffle is to control a card as mentioned in RRTCM, throwing in some jogs, do different variations and go on for maybe 20 minutes while watching tv without checking the deck. After that you should have perfect control of the card/s, but sometimes you will find the card somewhere else in the deck. It's only practice.

Sorry, sort of semi-hijacking the thread: Daryl mentions the milking shuffle (or milk shuffle). It is described in RRTCM, but not with that name. Anyone knows where that terminology came from? Cheers!