Prepration: Find a volunteer (One who won't mess up the trick). Teach him about the trick. Inform him not to tell anyone about your secret code (see below.)
Split the deck into several piles. Leave the room.
While you are out of the room your assistant will tell a person to pick a card from one of the piles. They call you back into the room. The assistant will have spread out the pile, face down, on the table.
Next have the assistant point to various cards. When the assistant points to the chosen card he will point to the middle of the card, while on every other card he will point to its corner. When you see him point to the middle of a card, you'll know it is the selection. Wait until he points to a couple more cards, then tell him to stop. Flip the correct card face up. Listen for applause.