A lawful good character upholds society and its laws, believing that these laws are created to work for the good and prosperity of all. He is both honest and benevolent. He will work within the established system to change it for the better, and strives to bring order to goodness that other good-aligned characters might pool their resources to better the world. A lawful good character combines a commitment to oppose evil with discipline. Most lawful good characters live by a strict code of honor, or by the rules of conduct set down by their deity. They will generally selflessly act by these codes even at the cost of their own life.
It must however be stressed that blind obedience to local laws is not required by the lawful good alignment. A paladin is not in violation of his alignment if he decides to take up arms against a usurper on behalf of the rightful king, for example, even if that means going against the sedition laws instated by the usurper.
It should be noted that a lawful good character does not actually have to obey laws, as intimated above. Lawful alignment means that the character prefers a structured life to any other; this typically means that a set of codified laws are followed.
An incorruptible enforcer, a ruler or politician who acts for the good of his people, and a heroic soldier who strictly obeys the laws of battle are all examples of lawful good characters.