Humans are social creatures. We are born in society, and roughly 99.9% of us continue to live in society. Civility is a term that seeks to capture what our moral obligations are as members of the societies we align ourselves with. The characteristic of civility manifests itself as a feeling of care and concern for the society of which one is a part. It is this sense of concern that compels a person who is "civil" to be mindful of the various obligations he or she has to their respective communities.
To be civil, a person must seek to uncover, to the best of their ability, what norms are in the common good, and what present norms may be in need of revision. Once a person has developed the appropriate sense of care for his or her communities, various behaviors will follow. For example, in the U.S., if a citizen is trying to do what is best for the common good, they will seek to elect representatives that represent this end.
On the surface, civility is not a particularly complex concept and characteristic to grasp. However, what counts as being in the "common good" is a horribly deep and thorny issue. One need not go any farther than issues of taxation, health care, and abortion to see that this is so. For these reasons, the most compelling, and for our purposes, pertinent demand of civility is that you be well-educated. Your job is to develop the kind of mind that is capable of navigating the murky waters of the common good.