A common use of the Scripture 1 Corinthians 6:19 is as a smoking cessation verse. In some ways I agree that this can be deduced from the verse as an application, but the primary meaning being who we give ourselves to during sex. The context will show this.
12"Everything is permissible for me"—but not everything is beneficial. "Everything is permissible for me"—but I will not be mastered by anything. 13"Food for the stomach and the stomach for food"—but God will destroy them both. The body is not meant for sexual immorality, but for the Lord, and the Lord for the body. 14By his power God raised the Lord from the dead, and he will raise us also. 15Do you not know that your bodies are members of Christ himself? Shall I then take the members of Christ and unite them with a prostitute? Never! 16Do you not know that he who unites himself with a prostitute is one with her in body? For it is said, "The two will become one flesh."[b] 17But he who unites himself with the Lord is one with him in spirit.
18Flee from sexual immorality. All other sins a man commits are outside his body, but he who sins sexually sins against his own body. 19Do you not know that your body is a temple of the Holy Spirit, who is in you, whom you have received from God? You are not your own; 20you were bought at a price. Therefore honor God with your body. 1 Corinthians 6:12-20 (NIV)
As we look at this text we see a primary meaning that sex is a physical union with someone else. This physical union should be holy since we are in spiritual union with God when he placed his Holy Spirit within us believers. Tobacco in and of itself does not make one unholy (Matt. 15:17-20) but does make one unhealthy. It is important to maintain the integrity of the passage that the Christians we teach think of this passage as being primarily about the importance of purity in the sexual relationship and not as a justification for Christian culture's extra-biblical social norms.
Smoking is reckless and foolishly unwise, but not immoral in the same primary sense as false worship, murder, adultery or theft. Smoking is immoral in the sense that it violates the virtues implied by the 10 Commandments. Jesus showed us in the Beatitudes that the 10 Commandments have at their root a moral virtue which is impossible to obtain without the grace of God. These implied virtues of the 10 Commandments must be taught after someone has clearly understood the primary teaching because in learning true morality, the plane sense must be master in the mind and heart before the implied virtues can really shine light on the deeper sins of the heart. Otherwise people can perceive that they can live a good life outside of the power of Christ. We are dependent beings needed God to empower us morally in the same way that his empowers us physically by providing us food, water, clothing, air, and other people. (We would not last 5 minutes without air; we can not last 5 minutes morally without God's power sustaining us.) Having said that, smoking is immoral in that it robs our loved ones of time in earth with them. It is immoral in that it destroys our health, makes us unable to work to provide for ourselves or our family, thus robbing society of our economic contribution. It is immoral in that it robs the kingdom of God of our talents, time and resources. For the married person, smoking is adultery since we are causing our spouse to loose access to our bodies in death. It is immoral in that it makes one a false worshiper when we let some earthly substance control us. Any addiction becomes the desire of our heart when we should be addicted to and enthralled with God.
If you want help someone stop smoking, consider exploring with the person you are counseling smoking cessation what effects smoking has on the three relationships of spiritual, social and self. In each of these, what effects does smoking have? Consider exploring what a vibrant and virtuous relationship with God, others and self looks like? Perhaps ask, in what ways does smoking effect each of those relationships? Since smoking is not breaking any explicit command of Scripture, we must explore how it is not virtuous. Disclaimer: Not everyone will be ready for this. Especially those who are saved by grace but trying to live the Christian life by works. These are Christians who understand that salvation is by grace alone working through faith alone but when it comes to Christian growth, they are trying to grow by works. Growth comes by grace working through faith also.
It is true we are the temple of the holy, immutable, loving, glorious, and ever long suffering God if we are a believer. We should use our body for only holy physical unions. In a secondary sense, we should use our bodies in a way that shows respect for the temple by keeping it healthy.