Most teenagers don't really listen to their parents. I was once a teenager and I admit that I also had a rebellious streak back then. My parents would often tell us not to drink alcohol, not to smoke, not use drugs; but I often hear my brothers talking back to them, "You drink and smoke, why can't I?" I guess, the best is to lead by example. No matter what we tell our children, if they see us doing something, they might imitate us. Just be a good role model and talk to them. And show them before and after images of people who abuse drugs like meth. That would deter them from touching the stuff (I hope).