Each guest is handed a diaper pin when they arrive. After everyone arrives, but before introductions, briefly explain to everyone what the pins are for. Usually there is a certain word or action, such as crossing the legs or ankles, that are off limits. If a guest catching another guest doing something off limits, then they take that person's diaper pin. If the person has more than one pin (from catching another person(s), then all of the pins are handed-over. Later in the party, usually just after the mother-to-be has opened her gifts, each guest is asked how many pins she has. The guest with the most pins wins.