Well, here's my basic outlook on what defines good/evil/vile/exalted/neutral.
Exalted: You go out of your way to right the wrongs of the world, up to and including not killing your enemies unless absolutely necessary, not causing unwarranted destruction in any way, not judging by race/alignment/whathaveyou, and POSSIBLY taking up sacred vows (of nonviolence being the most common), aspiring to lead by example. Misdeeds become easily forgiven provided the culprit demonstrates remorse, shallow or not (because redemption happens after a long way and you can't expect people to fully regret their choices at the drop of a hat).
Good: You're nice. Your methods for doing things include the least possible harm; your solutions to a problem always seek the least amount of sacrifices, even if they're harder that way. Yet, unlike the exalted, you DO accept that sometimes sacrifices must be made, and while you may not be happy about the prospect of killing, redeeming every enemy that comes your way is only practical in the long haul. You try to avoid bad thoughts but that doesn't mean you don't wish that darned kobold didn't wake up with a mouth full of fire ants.
Neutral: You're a regular person. Most people are neither concerned with the greater good nor dastardly enough to shaft others on purpose - at least not directly. Your conscience is somewhat secondary to your well-being, but more often than not that just means that you're not a hero, and would rather run and live to see another day than fight the evil overlord. On the other hand, if you run into an ancient tomb full of treasure... it's not like the corpses are using them, am I right?
Evil: You're a selfish bastard. You want things your way or no way. You get your jollies out of either watching people be screwed over or screwing them over yourself. You may actually have a heart or a conscience, but you simply don't care about them. Your first thought in a given situation is: how does this benefit me, or how do I keep myself from getting the shaft? That's not to say good or neutral people cannot be selfish at any given point - but in general, there will be at least a bit of hesitation for a second or two before they choose themselves.
Vile: Your every living second is devoted to giving people pain, grief and general unpleasantness. The most basic characteristic of a vile character is that he crosses the line of common human decency. A vile character is the kind of guy that would wear his enemies' scalp as a hat, or clothes made from the skin of his victims. Motivations for this kind of guy run the gamut from good ol' insanity to childhood trauma, but just as Exalted characters are quite unbelievable in the lengths they will go to in order to change things for the better (and are thus a little on the kooky side as well), there's something just plain wrong with the mind of a vile character. Remember that he need not cross EVERY threshold - some are more horrific than others, and most sociopaths fixate on ONE kind of line-crossing anyway.