As with some of the other posters in this thread, I develop Paladin codes based upon the deity (or Ideal) the player has chosen. Some are easy, some not so much. However, there is one thing that always remains constant. If you're a Lawful Good Paladin, Good > Law. If you're Chaotic Evil, Evil > Chaos, and so on and so forth. The Moral point is more important (In my opinion) to a Paladin than the Ethical point. The Moral point indicates your intentions. The Ethical point indicates how you achieve those goals (unless you're caught in a catch 22 situation, in which case Moral trumps Ethical).
An example of a Paladin code I've developed (and is a very common deity among my players), is the code of the Paladin of Ilmater.
1) A Paladin of Ilmater strives to be a paragon of Compassion. If the pain of others can be taken upon yourself, you are expected to do so, unless such aid would serve the cause of Evil and Suffering.
2) A Paladin of Ilmater is a beacon of Mercy. You must ask a defeated creature (Defined as a creature who surrenders, or has otherwise been rendered helpless/harmless) to give you an oath of surrender or noninterference in exchange for its life. If the creature breaks this oath to you, you can deal with the creature as you see fit without breaking your oath. This oath does not apply to irredeemable creatures (creatures that are mindless, undead, have the evil subtype and are evil themselves, or are otherwise marked by the Wrath of Ilmater; see below). This does not mean that you must deal non-lethal damage in combat (and creatures that you kill in combat do not cause you to fall), but it does require you to accept the surrender of any redeemable creature who gives it (Unless they are marked by the Wrath of Ilmater).
3) Those who have not been tainted by the touch of evil are to be protected from such corruption at all cost. Specifically, you are bound by your oath to protect the innocent, and children above all else. The failure to do so does not violate your oath, but a failure to act does.
4) The sick and the weak are likewise your charges, and a failure to protect and/or help them is a slight against Ilmater himself, as well as all Ilmatari (again, if this aid would further the cause of Suffering or Evil, then you are not required to render aid).
5) A Paladin of Ilmater is the Bane to any agent of Loviatar. A failure to act to stop an agent of Loviatar from bringing more pain into the world causes a Paladin of Ilmater to fall.
The Wrath of Ilmater: This is a special clause in your Paladin Oath. A creature marked with the Wrath of Ilmater is detectable by your "Detect Evil" ability, regardless of their actual alignment. They detect differently, and thus a Paladin may discern whether or not a creature of any alignment has been Marked. The Mark is a special brand that Ilmater places upon creatures who prey upon children. This mark is only placed upon child-murderers (not accidental death, but intentional), and paedophiles. If a Paladin of Ilmater learns that a creature has been marked, then he is bound by his oath to expose and judge these creatures accordingly. The only Judgement fit, in the eyes of the Martyred One, is Death. A failure to do so does not cause you to fall, but a failure to act does.
Special Note on the Mark: It is up to the DM as to whether or not a creature who has undergone an abortion procedure will receive the mark. In my games, I do not apply it in most circumstances (However, exceptions can be made). In my experience, it is best to simply not approach the subject, as it usually leads to OOC arguments.
