Firstly, In many countries like india and china has a large population.
I think you should not start with "firstly" "secondly" etc... in the beginning of a paragraph. You could do it better with a topic sentence which presents your general idea in that paragraph before you show examples.
What should government do or can do to reduce the amount of rubbish produced? Firstly, government can educate peoples through advertisement, newspapers and radio. So people can be aware of its harmful affect toward our environment. Secondly,By placing more and more rubbish bins in the public areas, government can reduce rubbish.
As I said, be careful when using adverb like those in bold form and capital letter, don't do it disorderly.
You could start with "The main point is,...", "In general / Grenerally...", "My first view is...", "One hand,... In the other hand,..."... or many other words or idioms. Be more flexible in using words :)