1. Tell a spectator that each card represents a number--A is 1, J is 11, Q is 12, K is 13, and the rest have their face value.
2. Tell the person to pick up the top card and place it face up on the table.
3. State its number and then count onto it enough cards to reach 13. For example, if the card is a Jack, say "Eleven..." and then deal two cards onto it while you say, "...twelve, thirteen."
4. Flip over this stack and set it aside.
Repeat Steps 2-4 until 13 cannot be reached with the remaining cards. Set these aside (if the count works out evenly, don't worry).
6. Have the spectator choose 3 piles. Remove all of the other piles and add them to the cards (if any) remaining from step 5.
7. Pick up the pile of cards remaining from steps 5-6, count off 10 cards and set them aside.
8. Have the spectator choose 2 of the remaining 3 piles. Turn the top cards on these 2 piles face up.
9. Add together the values of the two face-up cards, count out their sum from the cards you're holding and set them aside.
10. Have the spectator count the number of cards left in your hand.
11. Tell him or her to flip over the top card on the remaining pile. It is equal to the number of cards left in your hand.