You explain that you are going to expose the secrets of the fraudulent mentalists! You show a prediction card to everyone in the audience, except your volunteer audience member. another deck is shown to the audience – the one your helper is to select a card from. The deck is made up of all the same cards – the prediction card! The helper selects one card, but it’s not the predicted card! Fortunately, the card you first set aside now matches the selected card!
Easy to do!