They chose 4 random cards, openly and fairly. Those card turn out to be the 4 kings. Every time. Nothing quite compares with thefeeling of randomly selecting four kings in a deck, proving that you're on fire!
To take it even further, the next four cards they pick are the four aces! But, don't get too greedy too fast. The aces can easily turn back into regular cards to cover your tracks.
Easy to do, easy to learn and definitely gets the attention of your spectators.