Just memorize the three different hand gestures: 1 is called “goo,” which represents a stone. Simply clench your fingers into a fist. 2 is called “choki,” which represents scissors. Extend the index finger and middle finger, and close the rest of the fingers. 3 is called “par,” which represents paper. Simply extend all the fingers.
Participants say “Jan, ken, pon” in unison, then everyone displays either a “goo,” a “choki” or a “par.” “Goo” wins against “choki,” meaning a stone can break scissors. “Choki” wins against “par,” meaning scissors can cut paper, and “par” wins against “goo,” meaning paper can wrap up a stone. When the participants display the same gestures, they try again, saying “aikodesho” until a winner is found.
Many people think janken is a typical Japanese custom, but it is actually practiced in many different forms in other countries, too. It is said to have originated in China, but some say it began in Japan. Because of its convenience, janken is occasionally seen amongst daily life in Japan. It is indispensable for living in Japan and a Japanese culture.
(Source: Hiraganatimes)