When I was a kid my parents only let me watch PBS. No saturday morning cartoons -> no sugary cereal commercials -> no desire/nagging for sugary cereal.
Install adblockers on any computer your kids use. Cancel your cable television subscription. Deny these corporations the opportunity to pump their propaganda into your kids.
I still remember the hate I felt when I watched my sister turn from a really calm child to a screaming brat because of Hannah Montana. I don't watch the TV, now around 12 years.