Roleplaying and the nature of evil[I've got in mind a handful of roleplaying posts to make, this is the first one.]
One of the greatest mistakes ever made in D&D was the alignment system. Defining a character as good, neutral, or evil, is just an astonishingly stupid thing to do (lawful and chaotic slightly less so, but still). Why?
-It strait jacket characters into acting in a certain way, simply because of an alignment choice
-It encourages meta thinking rather than character thinking. Your character performs an action not because they are invested in it, but because they are "good"
-The nature of evil is nebulous, and encouraging players to take it as alignment produces a host of raving lunatics.
What is evil? I originally wrote this with a rather emotive example, but have decided to withdraw that. Hitler is the obvious example for evil. Yet he, as far as we know, did not believe his actions to be evil (he had some screwed up notion of manifest destiny and seemed to believe that he had only been wrong in thinking that germans were ubermen). He had rages, certainly, but could be kind, apparently had a form of love, and was certainly charasmatic enough to charm those around them.
Simply put, human beings are complicated. You can be hideously horrible to some people, and delightfully pleasent to others. Even sociopaths can be charming, although they live effectively amoral lives, and will kill without compuction, many of them are smart enough to realise that while they find no value in morality, others do, and its worth pretending that they do (this is similar to the realisation Belkar came to in Order of the Stick recently).
A completely untrustworthy lunatic who acts "evilly" at every opportunity will soon be unplayable. Not only does a character make little sense, they simply do not play well with others.
If you want to play an evil character, you need to think what has driven such a person to the extremes they go to. Look at, for example, the Operative in Serenity. There is a man capable of acts of utter evil, who has been completely indoctrinated to believe in the world he is building by his acts. We know that he will go to any length to defeat his enemies, often depraved ones, but can also be entirely charming whenever he needs to be. So you need to decide what drives your character. What is their motivation, their goal in life? What lines will they cross, and why? Who do they trust, and who do they hate?
Playing an "evil" character should not be a target. Ideally one should come up with a character concept of someone who happens to be "evil". Someone who, for whatever reason, has made choices almost all of us would disagree with, and is willing to keep on making those choices.
More than ever, as an evil character you really need to think "whats my motivation", something that should be on every roleplayers mind when their character needs to make a choice of any kind. When an evil character is about to do something wrong, you do need to question why- it can't be just because they are evil, it has to be something that drives the character to perform that particular act.