This is my absolute favourite card trick of all time, and I first saw it being performed by David Blaine. The main technique you need in this trick is the double lift. The trick involves using it twice to transport the card in the spectator’s hand with the one you are holding.
It’s so amazing that even if you get caught doing the double lift, and people know you are lifting 2 cards, they still can’t figure out how you did the trick.
Here is the performance and tutorial:
Now, David Blaine likes to make people pick a card before starting the trick. That makes the trick look way cooler, but it looks just as cool if you just do it with any random cards. The main effect is in changing the card in their hands.