The Effect: The magican shows a card to a spectator and gives it to them. The magican tries to guess what the card is. The spectator will think the magican was wrong but when they look at the card they see the card had changed and the magican was right!
The Secret: First you need to know what the top card in the deck is. Double lift and show the second to top card. Then give them just the top card. Make sure they don't look at it. Tell them to think of their card and your going to try to guess what their card is. Guess what the top card was that you saw before the trick. The spectator will say your wrong. Then tell them to look at their card and it will appear to them as it has changed.