This will help the DM clarify your characters actions and also provide a good reference should other players call into question your actions versus your ‘Code’.
Below are guides/ideas for building your code. Not everything here will apply but if it does then go ahead and add it to your code and give a brief description of its application.
Do you honor the laws of the land you are in or do you honor the law of your path/teaching/guild/Temple/ Deity?
How do you treat authority figures of another land? Do you obey them and honor their laws?
Are their any practices/ exercises/meditations, etc that your code requires you to do on a regular basis; i.e. prayer 1/day, tai chi, bless the morning sunrise?
Do you have to keep promises; honor your word? Can you lie, steal or cheat?
Are you required to give to charity? To assist in providing for the homeless, to provide healing for the sick, to tithe money to organizations? To give to Orphanages, hospices, helping out at a healing temple or to train others?
Are you required to spread the word of your order? To bring in new recruits or conversions?
Are you required to take a vow of poverty? Are you required to live humbly? Are you required to pay a portion of your personal wealth as a tithe to your guild/ teaching /path/Temple? Are there any other vows you are required to keep?
Does your code require you to be respectful and humble?
What are your views of nature? Is hunting animals ok? For pleasure ? For food? Clearing woodlands for farming and building material? Do you eat meat or are you a vegetarian?
Do you honor others laws even if you do not agree with them? What is your position on law breakers?
Can you sneak up on an opponent?
Can you surprise attack an opponent?
Do you have to announce yourself and your intentions before attacking an opponent? Do you offer an opponent the chance for surrender if possible?
Do you choose non lethal damage over lethal?
Do you always come to the aid of those being bullied, tortured or harassed?
Can you participate in covert operations; i.e. sneaking around the city, spying, sneaking over the city wall, hiding in shadows, moving silently?
Do you always accept pleas for help whenever given?
Do you adhere to a chivalrous code of conduct; must always be polite, courteous and helpful to people?
Do you have to defend the innocent? Uphold justice and the law (By justice and law, meaning the laws dictated by your sovereign/country/ temple/ guild etc)?
Must lawbreakers be brought to justice? do you have the right to judge others and or administer punishment if proper law enforcement is unavailable?
How will you treat your prisoners? In the middle of a dungeon?
Can you use poison? Can you torture? Can you use spells that are damaging? Are you prohibited from any type of spell casting or school?
At what point would circumstances allow to overlook your code? To save the world? a country? a friend? An innocent person? never?
Do you kill noncombatants? Even ones that will grow up to kill innocents (like a baby beholder)?
Can you attack unarmed opponents? What about opponents that are prone, flatfooted?
Are you allowed to hide from opponents?
Are you allowed to flank your opponents so that your rogue can sneak attack?
How do you view the Undead? Even the intelligent ones?
How do you view collateral damage? Fireballs in town? Missile weapons in crowded areas?
When you see an ‘enemy’ do you have to attack even if they have not provoked an attack?
Briefly describe your ‘codes’ ideals on the following? (if applicable)
What are the consequences of breaking your code? How will you know what's "right"? Do extenuating circumstances affect the penalties?
How can you repent for breaking your code?
1- You must not kill in anger or malice, but the good must be upheld. When all other options are exhausted, be quickly and merciful with your smiting of evil
2- You must not kill at all. This paladin would show mercy to even the most vile of demons, dealing sub dual damage at all times and restraining opponents after they have fallen unconscious. Makes for interesting role-playing if such a paladin is forced into a situation where by accident or intent they are forced to kill a BBEG. While perhaps not an evil or chaotic action, this would break the paladin's code and the paladin would have to atone for their transgressions.
Or for monks with a lawful neutral alignment:
1-Follow the laws of the land you are, in for it makes you an honorable person
2-The only law is that of the Path. Do not step off the Path and you shall find enlightenment, stray and obey the heeding of those off the Path and you shall never reach the end of the Path and true enlightenment.
If choice #2 was taken at character creation then actions that might be considered unlawful (ignoring town guards, etc) would be acceptable for this character so long as he or she staid on the Path (whatever that might be). This lets DMs show someone who is abusing this role-playing to act like a jerk and disrespect NPCs with authority to get back. If the player is happily going about doing chaotic things while sticking to the code, a member of the monastery might stop by and inform the character that it will soon be time for the Lotus Mind (or whatever) ceremony and unless he can wrap things up pretty quickly he'll miss out on a month long mediation period required by the Path. If you don't get your short term goals done soon, guess what? You've just strayed off the Path! Obviously this is a worst case scenario, but one can see it happening.