You could convince someone to quite smoking by telling them all of the side effects that come with smoking. It can cause lung cancer, respitory problems, and also takes years off of a persons life. It can also cause people to lose their teeth. Smoking is also highly addictive and takes up a lot of peoples time, second hand smoke can also cause diseases on the people they effect. A good article that can help is a magazine called gods view of smoking on jw.
Hope this helps