This is one of the "old time" legalistic points which was extant to a larger extent years ago, and usually two activities were linked together...smoking and dancing. There are NO VERSES in the Bible which prohibit either and after all, David danced. However, as others have stated, smoking does defile the Temple of God, so why do it? Then again, so does eating to excess, not getting enough exercise and any other activity which is unhealthy. It is very easy for non-smokers to say, "just quit" however, it is not that easy and for many is a very difficult struggle and that is understandable. If you are the smoker, I would start as soon as possible to get rid of this habit. Rather than spend money on doctors and fads, I would try it yourself. What I have found as a motivating activity to help me with self discipline is to quantify things and keep written records so you can compete with your self. In my case, its walking. Walking eight miles per day was a piece of cake for me and I am working my way back to that. I have charts which show how much walking I did per day and per week. I set a daily goal and try to reach it. The only expense is a pedometer for about $15 from Walmart. If I was a smoker, I would mark down a start date and time and add another 24 hours the when I surpass that time the next day. So then, in summation, smoking is NOT listed as a sin in the Bible but God has given us a Temple to take care of. Quiting smoking is can be a very difficult process which starts with marking down the day, date and time of your last cigarette and adding to those hours as the days go by. If you fall after two days, then you have a goal set to beat the next time. Most importantly, this process is under the umbrella of regular prayer to God to help you beat this and when that urge for a smoke starts building, you start building your prayers to Him. I wish you well!
1 Peter 2:12