The game requires three shells (thimbles, walnut shells, bottle caps, and even match boxes have been used), and a small, soft round ball, about the size of a pea, and often referred to as such. It can be played on almost any flat surface, but on the streets it is often seen played on a mat lying on the ground, or on a cardboard box. The person perpetrating the swindle (called the thimblerigger, operator, or shell man) begins the game by placing the pea under one of the shells, then quickly shuffles the shells around. Once done shuffling, the operator takes bets from his audience on the location of the pea. The audience is told that if a player bets and guesses correctly, the player will win back double his bet (that is, he will double his money); otherwise they lose the money. However, in the hands of a skilled operator, it is not possible for the game to be won, unless the operator wants the player to win.

When an individual not familiar with the shell game encounters a game on the streets, it appears that bets are being placed by numerous players, when in reality, most of the persons standing around a game are in league with the operator in a confidence ring. Shell game gangs generally prefer to swindle one "player" (victim or mark), at a time. The apparent players actually serve various roles in the swindle: they act as lookouts for the police; they also serve as "muscle" to intimidate marks who become unruly and some are shills, whose job is to pretend to play the game, and entice the mark into betting. Once a mark enters the circle of apparent players and faces the operator, the gang surrounds them to discourage an easy exit and to keep other pedestrians from entering and disrupting the confidence trick gang's action on the main mark. The job of crowding around also protects the operator from any incriminating photographs being taken of the act. The operator and the shills will try to get the mark into a heightened state of anger or greed. Once this is accomplished, one shill will pretend to disclose a winning strategy to the mark. It is all a ruse to get the mark to place a large bet.