Method:

You hand a whole deck to your spectator and tell him to shuffle it. You then tell him to count 26 cards which is half of the deck. As he/she is counting, you remember the seventh card. Then tell him/her to set aside the 26 cards counted. You then write your prediction to a piece of paper. Next, tell him/her to pick any three cards from the other half. After that tell him to put the other half on top of the counted 26 cards. Put the three cards in a row order face up. Tell him for each card how many will he add to make it 10. For example the three cards are a six, seven, and a king. You will add four cards to six, three cards to seven and zero to king as it is considered 10 together with jack or queen. You then add the three cards: six + seven + 10 (king) = 27. You then tell the spectator to get the remaining cards face down and count until the 27th card is reached. The 27th card is the card you predicted.

by : Enrico Lorenzo, source : http://card-magic.blogspot.com