A spectator is given a shuffled deck of cards. The spectator is allowed to shuffle the cards freely.
"You have there a shuffled deck of cards," the magician says. "The tools of a professional gambler. Let's see how good a card cheat you are. Deal us both hands of five-card-stud poker." The magician directs the spectator to deal the cards "Vegas style."
After the cards are dealt, the magician tells the spectator to turn over the two hands. It turns out that the spectator isn't such a good cheat after all -- the spectator has nothing good, but the magician has a royal flush!
This trick has a number of subtleties that must be carefully observed if it is to work properly.
Before the trick even starts, the magician removes the five cards of a royal flush (ace, queen, king, jack, and ten of the same suit) from a deck and sets them face up on the table. The table's covering should be such that its pattern makes these cards difficult to identify. The aces of all of the other suits are also removed and destroyed.
With these cards removed, the magician may freely shuffle the cards when the spectators arrive, and then lay them face up on top of the stack of cards on the table, thereby adding the stack to the top of the deck.
When the time is right, the magician hands the cards to the spectator and gives instructions on "Vegas style" dealing. "Vegas style" dealing involves dealing all of the players' cards and then dealing the dealer's cards. Because the magician is the only "player," the spectator is directed to deal the five top cards to the magician and then the next five cards into the "dealer's" hand. If you have arranged the deck correctly, you will have just been dealt a royal flush!
After the cards have been dealt, the magician may let the spectator shuffle the deck a few more times. After the trick is finished, the spectator will remember shuffling the cards and will probably misremember that they had been shuffled before the deal, making the trick all the more amazing when it is retold.
The only possible fly in the ointment (or "rusty edge on the fake guillotine," as magicians like to say) would be if the spectator, through sheer chance, dealt the dealer another royal flush. This is why the magician destroyed all of the other aces in the deck. Without them, this embarrassing circumstance is much less likely to occur.