How should we determine the final answer to policy questions posted here?
The moderator[s] endorse[s] an answer, and we go with that?
Whichever answer gets the most upvotes after some period of time? (How long?)
Whatever seems to be the sense of the community after some period of time?
Never finalize; just expect the community to follow whatever the current consensus is?
Once a final answer is determined, how should we codify it - make it clear that this is the policy around here?
Just accept (checkmark) the chosen answer?
Write up special Questions, tagged final-policy or something, that contain final policy decisions?
Add final policy statements to the FAQ, or link to them from there?
I think it depends largely on the nature of the policy. Policy decisions can become the community de facto "policy" on a few different levels:
- Majority Rule
A meta discussion reaches a very clear, majority-rules consensus. Sometimes the voting is clear enough to see that the vast, vast majority of users agree it should be one way or the other. The meta post is usually sufficient to cite the policy, but if it is a really high-level or commonly misunderstood situation, the policy could be annotated in the faq. But you should generally steer clear of documenting unduly-detailed, rarely encountered, or deep "insider" policies in the faq.
- Ad Hoc Convention
The community establish a convention simply by following a common behavior. This may start out by citing a meta discussion, but not necessarily. If the community simply follows a convention (and it goes unchallenged), it's generally considered "policy" for the site (for example, the choice of tags). The site itself usually serves as an example in lieu of explicitly codifying.
- Prior Policy
Some policies are passed down from previous sites on the Network. If a policy has become wide-spread and generally accepted on the other sites, a future site would have to make a pretty strong case that they truly need a different policy. We want a consistent experience for the users. The per-site metas are usually sufficient to cite these policies, but they can be brought up and re-cited here.
- Administrative Policy
Some policy decisions are passed down by the staff based on philosophical beliefs, or administrative and technical considerations. The larger issues are typically documented in the Stack Exchange blog. More detailed issues are typically documented over at Meta Stack Exchange.
The best statement of "policy" is by keeping the site clean of unwanted behaviors. Community self-moderation and vigilant enforcement are the key here. Users are more likely to imitate the behaviors they see on the site rather than reading through some codified compilation of "policy." No broken windows.
Broken Window: It’s pretty clear now that the broken windows theory applies to community sites as well. The theory is that minor forms of bad behavior encourage worse ones: that a neighborhood with lots of graffiti and broken windows becomes one where robberies occur. I was living in New York when Giuliani introduced the reforms that made the broken windows theory famous, and the transformation was miraculous. And I was a Reddit user when the opposite happened there, and the transformation was equally dramatic.
Robert did a great job answering your first question, so I don't need to.
As for the second, one approach is to add the faq tag to the meta post in question. If the situation later changes, it's easy enough to remove a tag.