The desire to quit smoking comes naturally. Often it can be provoked by a combination of several factors: the appearance of health problems, a feeling of disadvantage in comparison with non-smokers, and of the aforementioned concern for one's environment.
But even this is not a guarantee, often a toggle switch clicks in my head, and I do not want to smoke. Someone spends a month, two, half a year, someone lasts for several years, someone - until the end of their life.
It is almost impossible to force someone to quit smoking, but you can support those trying to quit with any available ways.
Stephen King has a story about smoking cessation - Quit Smoking Corporation. The essence of the method was that the smoker quit not for himself, but for the benefit of his loved ones.
A smoker, by and large, does not care what harm smoking does to his own body. He either does not believe that something can happen to him, or he accepts responsibility. But we often worry more about our loved ones than about ourselves, and dedication is more effective. Therefore, if you demonstrate that smoking directly harms loved ones, strong motivation immediately appears.
If you do not take such extreme examples from the story, then people sometimes quit smoking when they decide to have children.
Also some reward will help to quit smoking. I heard that in some companies they made a salary increase for those who quit smoking.
Cigarette smoking is an addiction, 99% psychological. It will not work to deliberately get into the human unconscious, where the root of the problem is.
Every drug addict knows about the harmful consequences of use and the rejection of it by society, but few people are stopped. And the legal status of smoking cigarettes complicates everything.
From personal experience, if you insist that a person quit smoking, or scare you with horror stories about lung cancer, you will only provoke negativity in your direction or encourage you to try , which is highly likely to turn into failure and subsequent lies.
You can advise a person to read the rather popular book by Alain Carr, "The Only Way to Quit Smoking Forever", in which all myths about smoking and the tricks of smokers themselves to justify their addiction are broken .