The general guidelines use by parents, grandparents, and teachers to motivate children towards correct behavior. It is the principle that we will do what we don't want (i.e. exercise) in oder to be able to earn what we do want (i.e. eat more at the dinner party.) In the fields of Behavior and Psychology, this is known as the "Premack Principle." This is what happens when you tell your kids they can play video games after they finish their home-work.
1) "Grandma's Rule is that you eat your vegetables if you want dessert."
2) "Grandma's Rule is that you clean your room before you go outside and ride your bike."