You need a deck of cards from Las Vegas that have a hole punched through the deck. The hole is usually in the center off to the left a little bit. Make sure all the holes in the cards are lined up so that you can see through the deck. Then tell your spectator to pick a card and memorize it. You then take the card and put in the deck(make sure that the hole is on the right side of the deck) You then can go through the deck and find the card that the hole is off to the side. When you get better at this you can start shuffling the cards but make sure that the holes are lined up when you shuffle. This trick can also be done if you have a deck of cards that the back of them are not symetrical in other words if you lined them all up and one was put in the deck the wrong way.