Answer:
It depends on what you want to convey through the essay. What is the message you are trying to convey? Does smoking in public create an image? Does it affect the health of the public around with secondhand smoke? Question should be expounded up on a little more for a better answer. Once you get what you want to convey though (say it's on how it harms the environment, nonsmokers, and the smoker themselves) then you also need to say "why" or "how" (which will end up being your topic sentences for the rest of the essay) so an example is " There are many things that can happen when you smoke, for example, causing air pollution, causing diseases in nonsmokers, and finally causing harm to smokers themselves". And then after you get this, your paragraphs will be focused on the three things you mentioned-air pollution, diseases cause, and harm to the smoker.