There is probably no worse discipline technique than to make rules or give instructions and then neglect to enforce them. Most parents fall into this trap when they repeatedly warn, threaten, and plead with their children, but don't take any action.
A good example of this is a mother and son I once observed at a meeting. The son was sitting behind his mother and was kicking her seat. She looked back and told him to stop. He kept on. She turned around and snapped, "I mean it! Stop kicking my seat!" He continued. Again, she turned around and said, "I'm not going to tell you again! Stop kicking my seat!" He persisted. Then she pleaded. "Mikey, please. Don't kick my seat anymore." This saga continued throughout most of the meeting. The boy obviously knew from experience that his mother was all talk and no action.
When you give children a warning or command, but then don't follow through to see that it’s obeyed, it teaches them that there’s really no reason to obey you. Why should they? They know they can usually ignore you and get away with it. And even if you do occasionally follow through, they know there’s a good chance that nothing will happen to them. It’s a gamble, and it’s worth the risk.
The solution? Be consistent! When you give a warning or command, consistently follow through to make sure your instructions are followed.
To learn more about being consistent, read Proactive Discipline: A Parent’s Guide.