Be consistent in implementing your rules and discipline.

It is a proven fact that when rules and discipline are implemented inconsistently, it has the opposite effect, and reinforces the opposite usually undesirable behavior. One example: the household rule is that the child must finish all of their dinner if they are going to get to eat a treat for desert. Bending on this rule, even if infrequently, teaches the child that they don’t have to finish their meal to get their reward. And it sets you, as the parent, up for potential begging, power struggles or tantrums.