In essence, a good Christian must be a generally good person. Virtue does not only exist in matters of faith, but is evident in every aspect of a person's life. So good Christians not only need to learn the truth about God and Jesus, and treat other Christians well, but they must be exemplary citizens of their community and the country.
Basically, one who has learned to follow God faithfully knows how to follow the rules and customs of society well also. And, one who has learned to follow the rules and customs of society will more naturally and easily follow the laws of God. These habits of character build upon each other, leading to strong faith and a strong example of good, prudent living.