AD&D 1E PHB: Chaotic Evil: The major precepts of this alignment are freedom, randomness, and woe. Laws and order, kindness, and good deeds are disdained. Life has no value. By promoting chaos and evil, those of this alignment hope to bring themselves to positions of power, glory, and prestige in a system ruled by individual caprice and their own whims.
Lawful Evil: Creatures of this alignment are great respecters of laws and strict order, but life, beauty, truth, freedom, and the like are held as valueless, or at least scorned. By adhering to stringent discipline, those of lawful evil alignment hope to impose their yoke upon the world.
Neutral Evil: The neutral evil creature views laws and chaos as unnecessary considerations, for pure evil is all-in-all. Either might be used, but both are disdained as foolish clutter useless in bringing maximum evilness to the world.
AD&D 1E DMG: Good and Evil: Basically stated, the tenets of good are human rights, or in the case of AD&D, creature rights. Each creature is entitled to life, relative freedom, and the prospect of happiness. Cruelty and suffering are undesirable. Evil, on the other hand, does not concern itself with rights or happiness; purpose is the determinant.
AD&D 2E PHB: Good characters are just that. They try to be honest, charitable, and forthright. People are not perfect, however, so few are good all the time. There are always occasional failings and weaknesses. A good person, however, worries about his errors and normally tries to correct any damage done.
Remember, however, that goodness has no absolute values. Although many things are commonly accepted as good (helping those in need, protecting the weak) Different cultures impose their own interpretations on what is good and what is evil.
Evil is the antithesis of good and appears in many ways, some overt and others quite subtle. Only a few people of evil nature actively seek to cause harm or destruction. Most simply do not recognize that they that what they do is destructive or disruptive. People and things that obstruct the evil character's plans are mere hindrances that must be overcome. If someone is harmed in the process... well, that's too bad. Remember that evil, like good is interpreted differently in different societies.
Lawful Good: Characters of this alignment believe that an orderly, strong society with well-organized government can work to make life better for the majority of the people. To ensure the quality of life, laws must be created and obeyed. When people respect the laws and try to help one another, society as a whole prospers. Therefore, lawful good characters strive for those things that will bring the greatest benefit to the most people and cause the least harm. An honest and hardworking serf, a kindly and wise king, or a stern but forthright minister of justice are all examples of lawful good people.
Lawful Evil: These characters believe in using society and its laws to benefit themselves. Structure and organization elevate those who deserve to rule as well as provide a clearly defined hierarchy between master and servant. To this end, lawful evil characters support laws and societies that protect their own concerns. If someone is hurt or suffers because of a law that benefits lawful evil characters, too bad. Lawful evil characters obey laws out of fear of punishment. Because they may be forced to honor an unfavorable contract or oath they have made, lawful evil characters are usually very careful about giving their word. Once given, they break their word only if they can find a way to do it legally, within the laws of the society. An iron-fisted tyrant and a devious, greedy merchant are examples of lawful evil beings.
Neutral Good: These characters believe that a balance of forces is important, but that the concerns of law and chaos do not moderate the need for good. Since the universe is vast and contains many creatures striving for different goals, a determined pursuit of good will not upset the balance; it may even maintain it. If fostering good means supporting organized society, then that is what must be done. If good can only come about through the overthrow of existing social order, so be it. Social structure itself has no innate value to them. A baron who violates the orders of his king to destroy something he sees as evil is an example of a neutral good character.
Neutral Evil: Neutral evil characters are primarily concerned with themselves and their own advancement. They have no particular objection to working with others or, for that matter, going it on their own. Their only interest is in getting ahead. If there is a quick and easy way to gain a profit, whether it be legal, questionable, or obviously illegal, they take advantage of it. Although neutral evil characters do not have the every-man-for-himself attitude of chaotic characters, they have no qualms about betraying their friends and companions for personal gain. They typically base their allegiance on power and money, which makes them quite receptive to bribes. An unscrupulous mercenary, a common thief, and a double-crossing informer who betrays people to the authorities to protect and advance himself are typical examples of neutral evil characters.
Chaotic Good: Chaotic good characters are strong individualists marked by a streak of kindness and benevolence. They believe in all the virtues of goodness and right, but they have little use for laws and regulations. They have no use for people who “try to push folk around and tell them what to do.” Their actions are guided by their own moral compass which, although good, may not always be in perfect agreement with the rest of society. A brave frontiersman forever moving on as settlers follow in his wake is an example of a chaotic good character.
Chaotic Evil: These characters are the bane of all that is good and organized. Chaotic evil characters are motivated by the desire for personal gain and pleasure. They see absolutely nothing wrong with taking whatever they want by whatever means possible. Laws and governments are the tools of weaklings unable to fend for themselves. The strong have the right to take what they want, and the weak are there to be exploited. When chaotic evil characters band together, they are not motivated by a desire to cooperate, but rather to oppose powerful enemies. Such a group can be held together only by a strong leader capable of bullying his underlings into obedience. Since leadership is based on raw power, a leader is likely to be replaced at the first sign of weakness by anyone who can take his position away from him by any method. Bloodthirsty buccaneers and monsters of low Intelligence are fine examples of chaotic evil personalities.