By explaining what they did, and why they need to go through with this punishment.
Explanation:
Parents often yell, or loose their tempers. It's better to stay calm, never ever get physical, and keep your voice normal but commanding. Explaining the timeout could help a child understand why their in trouble. I was often confused to why I was being punished, and my parents never explained, so it would keep happening until they finally told me what it was.