Setup: Before you start the card trick, find the two black 6's and the two black 9's. (The 6 of Spades, the 6 of Clubs, the 9 of Spades, and the 9 of Clubs.) Take the 6 of Spades and the 9 of Clubs, and place one of them on the top of the deck and the other on the bottom. Keep the 6 of clubs and the 9 of spades separate.
Trick: Show the deck of cards to your victim. (The person you are showing the card trick to.) Hold the 6 of clubs and the 9 of spades in front of the person. Ask
hem to tell you what cards they are. They will say the 6 of clubs and the 9 of spades, of course. Ask them if the are sure. They will say they are sure. Hold up either of the cards and ask them what card it is. After they respond, place that card in the middle of the deck. Now do the same with the other card.
Once both cards are inside the deck, place it down on the table, and tell the person to tap the deck three times. After that ask them if they have any magic card trick dust. If they say, no say you will loan them some and reach into your pocket and pretend to sprinkle dust on the cards. If they say yes, tell them there's no such thing as magic card trick dust. Now rub your hands together and blow on them so your fingers are slightly moist. (This is important.)
Pick up the deck by putting your thumb on top and your other fingers on bottom. Hold the deck very lightly. Swing the deck back and forth, and on the third swing throw the deck to your other hand, but make sure you hold onto the top and bottom card. Your moistened fingers will help.
Ending: After all that, your victim will still remember the cards, but only vaguely. When you show them the 6 of spades and 9 of clubs that you "pre-placed" they will be astounded, unless they have an awesome memory.