Preperation: Get an accomplice, and tell them the trick.
1. Ask your accomplice to leave the room or area.
2. Turn nine cards face down, three by three.
3. Have the spectator(s) pick a card.
4. Once they have chosen a card, have someone tell your accomplice to return.
5. Now you make a series of taps on the cards, anywhere from five to twenty. (You can always change the amount to fool your spectators.) The signal you give your accomplice is where you tap the first card. This tells him/her which is the chosen card. If you tap the first card in the middle, that signifies the middle card in the three by three setup; if you tap the first card in the upper right corner, it signifies the card in the upper right of the setup, and so on.
6. Now all that is left is for your accomplice to amaze the spectators by choosing the exact card.