In SET, each card contains up to 3 objects, with all of the objects on a card having the same color, shape and shading, e.g., two purple shaded ovals. Colors, shapes, and shadings come in three different types: green, red and purple; oval, diamond and squiggle; and solid, shaded and outlined.

All players go simultaneously and try to claim sets of cards in a single pass through the deck. A set is comprised of three cards that are either all alike or all different in each attribute. For example, if all three cards have the same number of objects, but three different shading , shape, and colors, then those cards are a set; if two of the cards have a common attribute that is not shared by the third, they are not a set.

To play, one person takes the deck and places twelve cards face up. The first person to spot a set takes those three cards; if the player was mistaken, then this player cannot claim a set until after another player has done so. After someone has claimed a set, the cardholder puts out three more cards. (If all players agree that no sets can be claimed, then the cardholder places three more cards. These cards aren't replaced after someone claims a set.) Whoever claims the most sets wins the game!