The Pinky Break
The magician squares the deck so it appears that the spectator's card is lost in the middle, but the card's location is actually being marked by the magicians pinky.
How It's Done
Hold the deck in the Dealer's Grip with your left hand. Put pressure into the back of the deck with your pinky to separate the deck just slightly where the card you want to keep track of is. From the spectators point of view the pack should appear to be square, but from the magicians eyes the separation is visible and it is easy to cut to the desired location. The pinky break can also be used to separate just two cards from the deck making the double lift easier.