Tell your child that you want her to practice polite trick-or-treating. Use a small cardboard box or even an old Tupperware bowl you don't mind sacrificing for this prank. Cut a hole in the box or bowl that's just big enough for you to put your hand through. Tape a piece of tissue over the hole and fill with candy. When your child is ready to practice, hold the bowl with one hand and as she reaches in pop your hand through the tissue-covered hole and give her a good tickle and giggle.