What are some good solutions to make my teen stop smoking?

Recently, I saw my teen (14 y/o) smoking in his bedroom. I think it was his first time because I heard him coughing alot. I made him sit on a chair and talked to him about the danger of smoking (I told him since he was 4 to never smoke). But during the discussion, he was like "... yeah yeah...." "I know that already dad..", etc. So... any suggestions?