This simple card trick can be found online and was performed by Lance Burton using giant cards on national television. If that isn't enough endorsement for you, I don't know what is.
Five cards are shown and a spectator is asked to mentally choose one of the cards. The magician takes the cards, removes one, and shows them to the spectator again. Sure enough, the thought-of card is gone!!!!!!
This is what is known as a psychological force. The magician knows what card to take away because, frankly, given five cards everyone will always pick the same card the first time they are given the opportunity. A different card will be chosen on the second attempt, but again everyone will pick the same second card. The same deal holds for the third card.
All a magician has to do is know what card the spectator will pick (easily enough found by asking, "if it were me, what card would I pick," since everyone chooses the same). The magician must also make sure that everyone viewing the trick has seen it the same number of times, or it throws the whole thing off.