(in old man voice) Come back here you little whipper-snappers....Why...when I was your age..(insert old-man comment about walking up hill to school here)

Seriously...I've got 4 kids. They do things on a daily basis to test their boundaries. Whether its drinking from the milk carton or taking just a few more steps further down the street than they're supposed to before looking over their shoulder to see who's watching. I believe the true technique with kids is to set boundaries and then make them extremely aware of the consequences of violating those boundaries. Every so often they just have to be reminded. Just my 2 cents.