Zach over at RPGBlog choose alignment for his Friday topic.
Even back in the day, I never used alignment much other than an indication of personality. What critical was your allegiances. Which god you worshiped, your liege, your patron, or what organization you belonged. Even players that played freebooters had to take the concerns of the local culture into account.
I found that properly presented this system was easier and more fun for the players as the consequences of actions were easier to for them to determine. Forswearing your god was much more obvious than determine whether an action was Lawful Good, Neutral Good, or Lawful Neutral. The same for betraying a liege, cheating a patron or neglecting your duty to an organization.
Back when I did first did this for AD&D I didn't much about the history of D&D. But now I realize that although more complex my system of allegiances was more in the spirit of the oldest version of D&D with their system of Law-Neutral-Chaos. If you read the First Fantasy Campaign you will set the three alignment system very much represented factions. Granted the Chaos were never very nice people.
To me nine alignment system was more useful as a description of a character's personality. As a useful indicator of a character's general tendencies. When I switched to Fantasy Hero, and later GURPS ; the roleplaying of motivations and personality assumed center stage. My old allegiance setup came along almost intact.
As for the mechanics they were simple. In-game loyalty was rewarded with in-game resources. Consequences came with disloyalty. My attitude is similar to that of "The die fall where they may" except that I had to rule on the various attitudes. Sometimes my decisions didn't ring true but I learned and gotten better over the years.
In addition I don't punish players for not knowing background details that are only in my head. This is not the same as tricking them with a clever plot or ruse. When a background detail is important I will give them plenty of chances to learn what it is before the time it is really important to know. Sometimes it is done in-game other time in my Updates that I hand out from time to time that fill the players on some aspect of the Majestic Wilderlands.
The reason for this is that I think immersion is one of the strongest aspects of roleplaying games. That you as your character are in another world, another time. Second to that is being a different person than you normally are with different motivations and personality. This what makes 30 year campaign possible and drives us to game over and over again through a mosaic of situations, genres and time periods.