To children 10 years and older; Based on Michael Losier's book - Law of Attraction, the science of attracting more of what you want and less of what you don't.
Keep your words simple. Use the word vibe instead of vibration. Get your child to give you examples of negative vibes. He/she will end up giving examples that relate to not having a great feeling.
The three words. Use a light switch and tell your child, ON means having a positive vibe and OFF means having a negative vibe. In addition, make your child understand the difference and ask them if they want to learn how to change their vibe. Write the words DON'T, NOT and NO and explain how these 3 words can create negative feelings. Ask your child to give you examples when these words are used. Example, don't wear your shoes in the house.
Secret. Teach your child how to switch the light from OFF (negative vibe) to ON (positive vibe) and tell them it is a secret as they will remember it better. The secret is that each time they hear themselves saying the words don't, not or no, they could ask themselves "So, what do I want?' Use the examples your child gave you in step 2 and tell them to switch it to positive by using the question - So what do I want?