The deck is cut, the bottom half is turned face up and both halves shuffled together. The magician then ribbon spreads the cards to show that they are mixed up with some face up and others face down. The spectator is told to select a face up card and turn it face down in the spread while the magician isn't looking. The magician then shuffles the deck several times. The cards are spread again, but this time only the chosen card is face up!
Easy to do once you know the secret.