You stay one step ahead of them!
Audiences- especially children- love to think they've "caught" the magician by figuring out the trick. They'll think they've got you on this one, but they'll be WRONG and WRONG AGAIN!
And it's very, very easy for you to do. Nothing complicated to learn - if you can hold the cards in your hand, you can do the trick!
Show three cards, one each with a green dot, a red dot and a yellow dot on them. Place the cards into an ordinary envelope, make your magic gesture, and take out the red dot card and the green dot card. Tell the audience that the yellow dot card has also disappeared. Of course, they will shout out that it is still in the envelope. Let the card peek out past the sides of the envelope while telling the audience again that the card has vanished. Their shouts will get louder and more insistent! Finally, say "You think the yellow dot card is still inside the envelope?" and take the card out. The card says WRONG!
Now the crowd will shout "Turn it around!" You can spin the card around, you can turn your self around, and they will get louder and louder. Finally, say "Oh, turn it around THIS way?" and you turn the card to show that the back of the card says "WRONG AGAIN"!
Great trick for kids shows when you want to get a LOUD reaction! Also works really well for ministry magic shows, anti-drug or anti-bullying message shows, and traffic safety routines.