Alignments
The subject of character alignment can cause a lot of discussion and disagreement whenever it is brought up. It seems that the ideas behind good-or-evil and lawful-or-chaotic can be quite subjective, to the point where alignments are generally ignored except where the system mechanics demands it, such as restricting classes or spells to certain alignments. The idea of what makes someone 'lawful' seems to be confused with the idea of 'law' itself, and is largely semantic in nature. Wizards of the Coast have published an article describing in more detail what it means to be lawful in the scope of D&D, which is one of the best guides I have read on the subject.
I would have to agree with what is discussed in that article. Being lawful does not mean that you have to follow the law. This is not immediately obvious, until you realise that the polar opposite of 'lawful' in the game is 'chaotic', not 'unlawful'. Rather than trying to grasp what 'lawful' means, it may be better to understand the ideas behind the chaotic alignment and then deducing from that what the opposite of that alignment would be. There is an amusing quote, which I cannot place, that the most predictable players in a D&D game are the chaotic ones. Again, this probably results from a misunderstanding of what the alignment means. It is not simply a matter of not following the law, which would be predictable, but rather to follow whims, not to be tied down to doing something the same way simply because that's the way you did it last time.
Following on from that, we can see that being lawful doesn't mean something as simply as following the law. The lawful alignment is more about order and predictability than staying within the law of the land. A lawful character will plan, and approach similar situations in the same way each time. He will search for order and routine in his life, even if it is as little as the way he dons and removes his armour in the morning and at night when he is out adventuring, when there is little room for routine. When trying to get some information out of a captured enemy he will use the same techniques. If he finds torture to be effective, he will torture to get the information; if he prefers to get the information from bargaining, then that is what he will do. Torturing someone doesn't make you chaotic any more than flipping a coin to work out which fork in the road to take makes you good or evil.
After thinking about the lawful-or-chaotic axis it would be easy to think that the good-or-evil axis would be simpler to agree upon. This does not tend to be the case, though. Is the good alignment something that is absolute, or is it relative? For example, is the death of an evil creature an inherently good thing, or are there occasions when it could be evil? The Book of Exalted Deeds and Book of Vile Darkness provide some good examples that while good and evil are not absolute they are also not relative to the person; rather, they are relative to the situation. A good character cannot then kill anything evil on sight, with no justification. This would be a form of genocide and not a good act at all. Just because the character views a race as evil does not make them a blight on the world to be removed. A character that attacks anything without question simply because of alignment would more properly be classed as psychotic, as they would be killing without provocation or justification.
And it works both ways. An evil character would not kill good characters or creatures on sight, just because of their alignments. It is more reasonable to assume that a character should find out someone's intentions or motives before deciding on a course of action. An evil mage would not necessarily try to kill someone intruding in his tower, but may ask what they are doing there and why. He may well then use force to remove them from his tower, but it is unlikely it would be his first course of action. In just about most situations, anyone who attacks or kills on a whim would be considered unstable or psychotic and would be the exception, not the rule.
Intelligence and reason play a role in this as well. A beast of low intelligence, around an ability score of 3 or lower, would be acting on instinct more than reason, and it is quite probable that it would attack anything it perceived as an enemy, threat, or food. Even then, it would not be likely to attack its own species or other animals that it benefits from. There are societies in the animal world as much as with humans. Once you get above an intelligence score of 3 you get more in to the realm of reason, and this is where evil characters will start to weigh up the consequences of their actions. Of course, at ability scores below 8 you will have characters making bad decisions and unable to realise the repercussions of what they are doing, so you may get a more violent version of evil. With higher ability scores of 15 and above you will get the opposite, where evil characters not only fully understand the consequences but can manipulate the situation, getting other characters to do their work unwittingly. They will not resort to violence as quickly as those with low intelligence ability scores, but use words and reason to greater effect. Evil doesn't mean violent, nor does it mean stupid.
A good working description of the evil alignment is that the end justifies the means. This does not mean that the end justifies any means, though. In a hack-and-slash adventure you may well find that killing someone is the easiest way to get what you want, but that does not mean that the evil character has no other way to achieve his goal, or that it is the correct course of action to choose because he is evil. Conversely, a good character believes that the means is more important than the end. Again, this doesn't mean that a good means can justify an evil end. There needs to be a vision of the greater good, and this can allow bargaining with evil people should that lead to, for example, safe passage through a kingdom so that a cure for a plague can be reached in time. It can also be seen that a lawful good paladin who enters a town of good alignment but whose laws allow slavery does not have to accept slavery as being right, nor be prevented from trying to change the situation. As long as he sees all forms of slavery as wrong and tries to correct the situation through predominantly peaceful means with a view to freeing the slaves his lawful good alignment won't be compromised.
In conclusion, alignments can be easily misunderstood, but with a bit of discussion between players and the DM and some understanding of the concepts behind each of the axes it is possible to use them to enhance a game. They can provide a greater sense of tension between characters, rather than an excuse to go on a killing spree.