Method

1. Shuffle the deck any way you want. Doesn't have to be any sort of special deck.
2. Have the spectator pick 3 cards. Don't let them show you and have them hold onto the three cards. Tell them to memorize the cards well.
3. Deal out a pile of 10 cards on the right (pile 1), 15 cards in the middle (pile 2), 15 cards on the left (pile 3), and then the last nine in a separate pile below.
4. Have the spectator put one card on top of pile 1.
5. Tell them to cut pile 2 and put it on top of pile 1.
6. Have the spectator put one card on top of the smaller pile 2.
7. Have them cut pile 3 anywhere and place on top of pile 2.
8. Put the last card on top of the smaller pile 3.
9. Put the nine card pile on top of pile 3.
10. Put pile 3 on top of pile 2, then put that on top of pile 1.
11. Take the top four cards and put them on the bottom.
12. Tell the spectator to watch the cards carefully and tell you to stop if they see their card.
13. Start flipping the deck into two piles: one face up and one face down, alternating. Start with a face up card.
14. Once you've gone through the entire deck, pick up the face down pile and repeat.
15. Repeat until only three cards remain.
16. Turn the three face down cards over.
17. Tada! it's their cards!