I have worked out my own version of the alignment system that deviates a bit from the norm (or AD&D at least). It is point based and the concept is that when characters do something it has both a law/chaos and good/evil aspect. The law/chaos aspect has to do with the legality or civilization or society impact of the action, whereas the good/evil aspect has to do with the motive. Points are assigned based on the action and the motive. So for example, Robin Hood steals from the rich (illegal and therefore chaotic) and gives the the poor (motive is charity). Thus his actin is Chaotic Good. He gets -1 Law-Chaos and +1 Good-Evil, and so Robin Hood is (-1 , +1). As the Character do things in the world, if they have a moral or legal implication I ask them what the motive was and record and sum their total Alignment. Thus as the campaign progresses their Alignments change according to their Character's actions and motives. What I've found is that most Players play their Characters as neutrals, bouncing back and forth between law and chaos and good and evil. It takes actual focus and determination to pursue an alignment path. I also have it that at certain levels (say over 10 L-C, G-E) the Deities begin to take notice of them. An interesting side effect is that Alignment then becomes its own pathway to success (or failure), and low level Characters can still manage to amass Alignment scores that make them "Somebody". It's interesting. I like the way it works. The only problem with it is that it adds another bit of accounting that needs to be done during the course of tallying up Experience. Not a big deal, but then again, its another thing to remember to do. But that's really the only problem I have with it. Other than that, it really does add something a little special to my game. That said, thus far, I have not made extensive use of the Alignment System. I've been so busy working on various aspects of my project at various levels a few things tend to slip through the cracks. The use of the Alignment System has been, therefore, a bit spotty. I should, now that I think of it, get back to using the thing. It's not required, but it's a fun little doodad that I can use in a number of ways throughout the course of the game.
It also ties in, I should add, with my system of Tarot-Astrology which is represented by the backface card of my Elthos Tarot Deck. At that point the story about Elthos Alignment gets a bit involved so I think I'll leave that aspect for another day. This is already getting a bit tltr as it is. :)