I used to do a pretty good card force trick where I would look at the bottom card of the deck, and then I would tell them to point to that card, but not look at it, then I would look at the card, and tell them to pick that card, and then do it again. Then I would say I would pick the next card, and pick the bottom card. Then I would lay down all 4 cards and say "You pick this, this, and this, and I picked this", and the other person is just like wut.