I'd be happy to help. First of all, make sure you look through the free essays and articles we have here on our site; there's a wealth of information there!
How to approach the topic of smoking in public places depends on the emphasis you want your essay to have. For instance, you could talk about the law -- how it has changed over the years, what the trends are now. Are there any places where smoking is more restricted than others, or less restricted?
You might want to talk about the effects of second-hand smoking, or the rights of smokers -- or both! Decide what aspects of the topic are most important to you and go from there.
Once you have written it, I'd be happy to take a look at it for you and make more specific suggestions.
There are lots of articles about this topic in the Internet. You can google "smoking in public places", then read several articles with the same topic to get some clues for writing your essay. Open the introduction with a motivator. For example you can talk about the number of people who die from smoking each day. Then write the thesis statement and finally mention what issues are going to be argued in the body (Blueprint).
