Do you talk about good and bad choices as it relates to money?
The best way to teach young kids especially to make good choices is to offer two (only two) choices and hopefully they will make the correct choice but the wrong choice isn't a time for scolding, its a time for learning - a teachable moment.
You cannot start too early discussing the difference between needs, wants and wishes. This on-going discussion will prepare them for making good spending decisions in the future.
In the book, "How To Teach Your Kids About Saving, Debt and Investing", I outline what I believe are needs, wants and wishes.