A good citizen cares about his/her city. Not only politics and rules ( rights, duties) but the environment too. The create ways ti have a clean city. First, sure, they maintain their places clean and try to clean most the can.
In my neighborhood there's a group that all Sundays the people walk around the neighborhood and wipe the streets. Also they teach the community how to maintain a nice city.
I guess that to become a good citizen we need to love and accept our place, and the only way is to maintain it clean; it works if we have the intention to make it. It's healthy and help us to love and be proud of the city.