Card Trick
The spectator selects a card from a deck of cards and replaces it. The magician cuts and shuffles the deck. He then shows the top card (which is not the spectator's) and places it under a handkerchief, which is then handed to the spectator. With a magical pass, the card in the handkerchief switches places with the spectators card in the deck.
Trick Secret:
Have the spectator chose and replace a card on top of the deck. After they replace their card, give the deck a false cut. Follow this with a riffle shuffle keeping the top card on the top of the deck. Do a double lift to show some random. Roll the top card of the deck (their card) into a handkerchief, and hand this all to the spectator. From here on, be creative in revealing that the cards have switched places. You can even cut the deck when they see the cards have switched so if they want to see where the card they saw enter the handkerchief went, they will see it went to the middle of the deck.