I see it as kind of a funnel. First you decide how much participation you want to allow in the first place, and that's a big lever. Smaller niche communities are easier to moderate because a lot of policies are customs, meaning you don't need to make them explicit.
Another lever is related - decide how much you want to limit the kind of content. A like button is easier to moderate than upvote/downvote, which is easier than a poll response, which is easier than restricted markup, which is easier than allowing unsanitized html/js/sql. (I think there's a lot of unexplored territory between "poll response" and "restricted markup", in terms of allowing people to participate with the generation of content.)
Then there is distributing the moderation abilities themselves. Can users become moderators or only admins? Is there a reputation system? I miss the kuro5hin reputation system and would like to see more experiments along those lines.
And then finally you get to the hard stuff, the arguments about post-modernism and what truth is, creating codes of conduct, dealing with spirit-vs-letter and bad faith arguments, etc. Basically the "smart jerk" problem. I hate that stuff. I want to believe something simple like, as soon as you have a smart jerk causing problems, it means you've given them too much opportunity and should scale back, but I think it's not that simple.