One that I found effective is for me to just take the child for a car ride and talk. Some say it's the vibration from the car, others say it's the time away from any distractions such as TV, Video Games, Computer, IPod, etc..
Either way, my kids usually calm down and stop misbehaving after our car ride together.
I've included a photo below of one of my sessions with my son, in case you would like to use the technique.
I think this will work with grandchildren, nieces, and nephews as well.
(OK, it was just too funny not to post here...)