The magician selects four cards from a deck that has been freely shuffled by the audience. The four cards should all be the same (except for the suits, which should be different) -- the four aces, for example.
"Everyone has a distinct aura," the magician says. "And every time you touch anything, a bit of that aura rubs off. I, as a trained magician, have been trained in the magical art of viewing auras, and can see them where they have off rubbed. Here, I shall demonstrate."
The magician takes the four cards in hand, setting the balance of the deck to the side of the table. He then lays the four cards out parallel to each other in a neat row so that all of their faces can be seen.
"I will now turn my back. While it is turned, one of you should turn a card over. Don't tell me who will do the turning, give no sign what card was turned, and say not a word until I instruct you further."
The magician then turns around and waits until someone tells him that his instructions have been followed. Depending on the group, this may take some time.
After turning back to face the cards, the magician waves a hand over them and appears to concentrate deeply. In a moment, his hand comes to rest above the card that was touched and, amazingly, he names the card without turning it over!
The magician needs to both locate the card and identify it. Locating the card is simple -- it's the one that's turned over (the back is showing). Identifying the card is more difficult.
The value of the card can be easily arrived at if the magician remembers that all four cards have the same value. The magician simply looks at any of the face-up cards, remembers its value, and uses that as the value of the face-down card. This always works. It is automatic!
To divine the suit of the face down cards, the magician examines the suits of the face-up cards. Cards come in four suits -- diamonds, clubs, hears, and spades (easily remembered using the magician's acronym DitCHeS). The magician mentally eliminates the suits which are visible (face-up) on the table and knows that the remaining suit is the suit of the face-down card. All that is left is to reveal this suit and the previously arrived at value with great ceremony.
For a more miraculous feat, four identical cards and a joke can be used, but this increases the difficulty by 25% and requires significantly more mental calculation. The basic principles still apply, however.
If the magician's audience is familiar with the basic trick and the magician has a good memory, a variation of this trick may be used. The magician chooses three cards and lays them on the table. The magician then turns around and tells the audience to select an additional card and place it among the cards already chosen.
When this has been accomplished, the magician turns around and instantly names their chosen card by simply remembering that their card is the one card that is not one of the cards first put on the table. It's a miracle!
If the magician has trouble remembering what cards were initially selected, they may be secretly written on the palm of the magician's hand with a Sharpie marker.