Step 1: Set the Deck
1) Remove two sets of two cards from the deck. The color of all the cards must be the same. Each set must contain the same number or suit, depending on how you've grouped them. Black seems to work better, and I prefer using the 5 and 9. If you do the same, you will need to remove the 5 of clubs, the 5 of spades, the 9 of clubs, and the 9 of spades.
2) Place one of the cards on the bottom of the deck. In this example, I placed the 9 of clubs on the bottom.
3) Set the card opposite number AND suit at the top. Place the final two cards atop it.
Step 2: Begining Your Presentation
Step 3: Get the Viewer Involved
Sometimes, they'll try to put a card on the top or the bottom, so if they do, give them a "look" and ask them "Do you really want to put that card there?" Usually, they'll reconcider. If they don't, flat out tell them to put it somewhere else. Promise them it will make the trick more interesting. Most of the time, however, they won't try it anyway.
Have them square the deck.
Step 4: The Reveal
Grip the top and bottom cards between your thumb and first finger. Push your wrist back and 'throw' the deck (into a chair, preferably). The trick is to hold the top and bottom cards while losing the rest. Flip the cards over to reveal: Not the same cards! (Gasp!) Relax; most everyone will not notice the switch (especially if you're fast enough). Actually, I've never had anyone figure this out (the first time I showed them).