How can being a conscientious citizen help in curtailing government expenditures?
I think that you are asking how citizens can help to keep government spending down. I have changed your question to show this.
The answer to this depends greatly on what sorts of spending your government does. In general, though, individual citizens should try to consume as few government services as they possibly can. When the government offers services that the people do not need, they should simply not use those services even if they would like to.
For example, my brother's children attend a school where breakfast and lunch are free to everyone because of the high rate of poverty at the school. Parents who are not poor should not consume that service. They should not take advantage of this benefit being offered by the government even though it is in their own selfish interest to do so.
Conscientious citizens should consume as few government services as they can so as to keep government expenditures in check.