For:
1.Secondary smoking will impart more harms upon other people who do not even smoke themselves.
2.Public smoking to some extent soil the reputation of the city/country
3.It may cause environmental problems as people tend to dispose of the cigarette anywhere
4.Potential fire hazards
Against:
1.It limits the basic rights of freedom of the citizens
I suggest that you can consider different public venues (indoors,outdoors,etc) which can further help you argue your points =)