Early education and regular interaction with your kids will help you educate them about the ill-effects and the after affects of it. I have been a drug addict myself and I suffered quite a while for sometime but one fine day when I got admitted to hospital then my parents came to know about it.
Instead of expecting a regular reaction of getting beaten or scolding, they didn't do anything and they helped me and told me the effects of it.
I faced a lot of challenge while facing it but then gradually I left everything and now I lead a very healthy and normal life. Yes wasn't able to quit smoking but I did reduce it to 1/10th for the day and will leave it soon.
If anyone who is known facing this problem then you should immediately consult your doctor and approach parents as they will be the best guide.