Whenever he saw a young man smoking, Peter would walk up to him and say, "How old do you think I am?" The young man would try to guess, and invariably would guess a far younger age than Peter had actually achieved. (Peter was 90 years old at the time.) Peter would reply to the smoker, "Do you want to get to be my age?" and the young man would always answer, "I know, I know!" And put out the cigarette.
Or Peter would try another tack. "You know that smoking is bad for your health, right?" And invariably the young man would answer, "Well, we all have to die some time." "Yes," answered Peter. "But it's how you die that matters!"