To sign devil, form the number 3 sign with both hands as you hold each hand on either side of your temple (like the ears or horns of a mammal). Then as you pull both '3' hands down a short distance, bend the fingers that are sticking out, then repeat the gesture and motion a couple of times. Be sure to make a serious face as you sign 'devil'.
Teach your baby or toddler the devil sign in the context of Halloween costumes and characters, or when your baby hears someone say, "Why, you little devil?!" as they go chasing the naughty kid around the block. While it is good to introduce popular cultural icons and staples to our kids, let us also be careful to teach the contrasting signs (angel-devil, good-bad) in the light of the behaviors that are good, harmonious and acceptable to society, versus the ones that are harmful and bad.
This is a useful flash card taught best in conjunction with the related holiday or costume signs, as well as with values or religious-themed education.