What parenting tactics do you use to educate your kids about the dangers of substance use?

I am not a parent, however, I am very close to my niece and nephews and I believe I have some influence on them and being a role-model to them is important to me. I want to lead by example. They see me workout everyday, eat well and see me live generally a healthy lifestyle which includes not smoking. They all take turns working out with me and during those times we talk about how to keep healthy. Topics of substance use comes up and I let them know the dangers of using and how substance use is not conducive with a healthy lifestyle.