Items required for the game included three small opaque containers, a token, and a flat surface. The game began with the perpetrator, often called a con artist, placing the token under one of the three containers, then quickly sliding the containers around until the container that held the token was uncertain. The object of the game from the mark's perspective was to guess which container held the token.
The secret of the game lied in the perpetrator's ability to perform sleight of hand with the token while shuffling the containers. They could thus ensure that the mark would lose no matter which container they picked, then slip the token into a different one.
Often, an accomplice to the con-artist would play the game to build the mark's confidence in the possibility that the game is winnable. In reality, the con-artist made sure that the token is under the predetermined container when the accomplice was playing.
Neelix and Tom Paris unsuccessfully tried this scam on The Doctor, in an attempt to prove their deceptive instincts had not dulled with time, after they were conned by Dala and Mobar. Later, however, after Dala and the others were successfully defeated, they again ran the shell game, this time tricking The Doctor with a technique known as "the old handoff," in which Neelix passed the tera nut used in the game to Paris without The Doctor noticing. Although The Doctor considered this "cheating", Neelix commented "We've still got it." (VOY: "Live Fast and Prosper")