To "Boo" someone you first need a little bag filled with anything from candy to candles, anything fun and inexpensive. Then you hang and little note on the bag saying that "You've been Boo'd". Also include the little poem about being "Boo"d and the instructions to keep it going. It's a fun fall activity to do to friends or neighbors. The "rules" state to do it to 2 people but you may just end up doing many more!