How to find motivation for friend to Quite smoking cigarettes help!?

On of my friends has been smoking cigarettes for almost 2 years now. He says that he wants to quite but he doesn't really have the motivation. Is there anything that i could do help get him to stop? I told him that i was going to start smoking until he stops (i was joking and wanting to see what he would do) and he freaked out on me. I really need some help here.