First of all, you should alert the smell of cigarettes from clothes of a teenager. Be especially careful if the smell is permanent, and all the questions the child says he was in the Smoking company. Also disturbing factors can be more frequent brushing, as well as the constant use of chewing gum.
To start, try to talk with the child. Explain that you care about him, tell us, what harm can it cause cigarette body, show pictures of lungs of a smoker. Often a Frank discussion will help you understand your child smokes or not, and then choose the correct action. Keep in mind that if the child confessed, it is not necessary to fall into the Creek, talk to him or her quietly. Remember, because you too were once that age and probably have tried Smoking.
If the child denies Smoking, but it constantly smells of cigarettes, then try to catch breath smell. If a teenager of pre-chewed chewing gum or candy, the smell may be absent. Then pay attention to your fingers - the smell of tobacco kept them much longer.
View the pockets, and backpack - if your child regularly smokes, he surely will be found cigarettes.
Please note on the company, in which revolves a teenager. If there are many smokers, it contributes to "herd reflex" who so love to follow Teens.
In any case, it is not necessary to punish a child for cigarettes. The most effective will be the same conversation.
And again. If you do smoke, and your child knows about it, then you will be much more difficult to talk about the ban on Smoking, because children take their cue primarily from their parents!