How to use essential oil appropriately to make sure I'm using it in a right way?

I reckon there is no one "right way" or appropriate way to use essential oils. In general, essential oils can be diffused, used topically, internally, and inhaled. The "appropriate" method for a person should be based on the essential oil and his/her preference, convenience, and health. For babies, extra care should be taken. I wouldn't apply essential oils directly without it being diluted nor would I let baby take it orally. Here's an interesting article you can read more about essential oils and appropriatee usage. http://www.livingwhole.org/the-right-way-to-use-an-essential-oil/