This trick makes you seem like an unbeatable magician. It’s a great one for an audience rather than just one or two friends and all you need is a pack of cards.
The idea of the trick is that your friend chooses a card from the deck of cards, memorizes it, places it back into the deck of cards and you shuffle the cards up, like a standard magicians card trick. Then, you start dealing the cards on to the table face up. After you’ve dealt quite a few cards, ask your friend “How much do you want to bet that the next card I turn over will be yours?”. The amount of cards already dealt on the table should satisfy your friend and they should be able to see that their card has already been put on the table and so they will agree, expecting you to lose. Then, turn over their card that is already on the table over to the non-picture side rather than the next one in the deck and watch their jaws drop as you flummox them all with your magic powers.
So, how do you do it? You need to know what the card at the bottom of your pile of cards is. This will become your key card. Next, allow your friend to pick a card, memorize it. Whilst they do this, separate the deck of cards where your friend took theirs from. Hold the top pile out to your friend and ask them to place their memorized card on top of this pile. Then, place the bottom half of the pile on top of the original top pile- this now means the bottom card you memorized is the card before your friends chosen card. Shuffle the cards a couple of times and then begin dealing the cards starting from the top of the pile. When you reach your key card, you know the next card you place down is your friends card- remember which one it is!
Place a few more cards down on the table. Then say your line “How much do you want to bet the next card I turn over will be yours?”. Then, instead of turning over a new card from the deck face up, you’ll turn a card already on the table face down- your friends card. You then win the bet!