Anyone trying to tell others to quit smoking loves telling them that the Marlboro man died of cancer caused by smoking. Does that help? I guess not. It is not a fact strong enough to make a smoker think about quitting. The other ineffective means of persuasion I have seen are the lame ads on TV. Quite predictably, they show the smoker and the people around them continuously coughing. As a kid I sometimes found the smoke from my dad's ciggy choking (He quit years ago) but neither me, nor my dad was ever coughing. As a non-smoker I find the ads overdoing it. They lose credibility and I am sure no one, specially the smokers, takes such an ad seriously.
So what is effective communication? I have seen some ads in Australia with pretty hard-hitting messages and graphics. I am sure they will make smokers think about quitting. Why don't you go and search YouTube for those ads?