bell on a string, or bell and string to attach the bell to,
Turn the cup upside down.
Cut a small hole in the top (bottom normally) of the cup.
Thread the string attached to the bell through a hole.
Remember to leave part of the string inside the cup so the bell can swing back and forth.
Tie a half knot in the string near the cup's opening to keep the string
from sliding back into the cup, or use tape to secure it.
Decorate the cup with stickers.
References / Source:
GSLC Pow Wow 2008