I'm thinking more about basic codes of behavior, not Papal Edicts or hundred-page dietary laws.

The codes of behavior I'm thinking of, like generosity, marital fidelity, chastity, rules against murder and theft, and other basics are indeed noted in major religions* but more importantly, they are enshrined in almost every culture on the planet.

I will certainly grant you that many peripheral cultural rules are useless, or even bad (treatment of women in some cultures, for example) but the basics are still there.

A good rule of thumb: Pay attention to the rules of behavior that are common to almost ALL cultures and civilizations. It's not a coincidence that the Golden Rule appears in different forms almost everywhere.

*The ironic part is that the important rules can be counted on the fingers of one hand. The most important statements of every major religion can be distilled to a few sentences. Heck, if you discount the ones pertaining to how God should be dealt with, it only takes six Commandments to cover almost all human relations. Again, if you disregard rules on how man deals with God, Jesus knocked it back to one, which is pretty much a rehash of the Golden Rule.