Invisible decks are trick decks of cards wherein an adhesive is placed on the backs of each card. This causes cards to stick together. The deck is arranged in a manner where cards are back to back and paired in specific orders. Decks like these allow you to perform the famous David Blaine trick where a spectator names a random card from the deck and he shows that only one card in the deck was face down--the card the spectator named.
Learn how these decks work. The cards are paired in specific manners. Every pairing equals thirteen. Spades are back to back with Hearts and Clubs are back to back with Diamonds. Aces are paired with Queens, Jacks are paired with Two's, and Kings are paired with other Kings.
Examples of pairings would be the Seven of Spades and Six of Hearts. Spades are paired with Hearts and the pairings have to equal thirteen.
Approach the spectator and hand her the deck of cards, still in it's box. Ask her to hold it up.
Explain the "connection" you feel towards her and how this will only work with her. Tell her you want to test the strength of this connection.
Ask her to think of a card, any card, from the deck. Tell her "not the Ace of Spades." Ace of Spades is the most commonly chosen card.
Have her name that card. Let's say she names the Eight of Hearts. Widen your eyes. Ask her to make sure she named the correct card.
Take the deck back from her and open it up in the direction of the value of her card, in terms of odd/even. One side of the deck is for odd cards and the other is for even. If she names the Eight of Hearts, you want the odd side because the paired card is the Seven of Spades.
Search through the deck for the Seven of Spades, explaining that all the cards in this deck are face up, except for one. Spread the cards as you search, being careful not to separate the adhesive pairs. Separate the adhesive at the Seven of Spades to reveal a facedown card.
Turn the face down card over. It will be the Eight of Hearts, her chosen card. While you used a trick deck, your spectator will think that you just randomly had a deck that had one face down card out of fifty-two, and she just happened to name it.
Act with this. Your acting is what will sell this trick.
Spreading the cards too violently will cause the adhesive to break and reveal more face down cards.