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.