EFFECT :
From a thoroughly shuffled pack, three spectators each
choose freely any four cards. Each of them mentally selects one
card. Performer, going to one of them and cutting the pack, says,
'Please put your card here,' and he holds out the lower portion of
the pack. 'Now drop your other cards on top of it,' he adds. 
He then openly drops the rest of the pack on top of these. He goes
through the same procedure with the other two persons and then
shuffles the pack. Asking the last person who replaced his card to
name the one he thought of, suppose it is the 6S, the performer
spells SIX, taking off a card for each letter and turns the next, it is
the 6S. He does the same with the other two. The value only is
spelt, the suits are ignored.

HOW IT'S DONE....
A key card is required, a short, a long or any kind of key
card you prefer. When the first spectator replaces his card you
have cut the pack including the key card. Drop the cut on top
openly and square up. Go to the second person, again cut at and
include the key card and have his four cards replaced, thus
bringing them on top of the other four. Do the same with the third
person. Finally cut at the key as before and shuffle the cards in the
right hand on the face of the lower packet, thus bringing the three
sets of four cards to the top of the pack. Begin with the third
person and ask him to name his card; if it is an A, 2, 6, or 10,
spell and take off three cards turning up the fourth; if it is the 4,
5, 9, J, or K, turn the fourth card; if it is a 3, 7, 8, or Q, pull the
fourth card back on the pack with the left thumb, take it off again
and show it as the fifth card. Hold this card in your hand as you
ask the next person to name his card-if it is a three- or four-letter
card drop it with the others on the table, but if it happens to be a
five-letter card put it back on top, making the spelling correct. Do
the same for the remaining card.