To Makesher,
I think a lot of young people see older people in their yeshiva smoking. They unfortunately look up to these older people and it perpetuates. I don’t think the hanhalah of the yeshivos do enough to discourage new smokers.
Now, I’ll address your question of how to encourage smokers to quit. First of all, don’t approach someone who you don’t know -they’ll never accept anything from a stranger. You can approach someone you know, but not with something like -Did you know smoking is the leading cause of cancer?, this will just alienate them. What you can say is -Oh you smoke- how long have you been smoking? They will probably tell you. Then you say -have you tried quitting? They will either answer yes or no. If they answer yes, they will probably go into a whole story about how they tried and failed and so on. Wait till they are done and then say -You know you should go see your doctor, they have a lot of new ways to help people quit. Even if the guy tried a few ways, he probably didn’t do all of them. Some places have an organized team to help people quit consisting of a therapist and a clinician. One to tackle the psychological component and the other to tackle the physical component.