How do you convince somone to quit smoking?

For a person to quit smoking, it has to be something that him or herself has made the decision to do. One cannot make or convince a person to quit smoking. He just has to realize that if he wants to stay around to see his kids grow up and be able to do things with them once they are adults, than the smoking must go. But again smoking is a rather hard habit to kick, I know, since I've been through it. Luckily I have had the willpower to stay smoke free for quite awhile now. If and when he decides to quit than he'll need his friends and family to be his support group, but be aware that when one is kicking a smoking addiction it can make the person rather cranky.