I think newcomers miss out on a lot of good existing answers because we don't rather forcefully suggest they look for duplicates when they ask a question.
How good is the question search, and could some kind of structural overview make it even better?
I don't mean to go all 'Clippy' on them ("You appear to be composing a suicide note. Would you like help?" http://knowyourmeme.com/memes/clippy). But it might be fruitful to immediately run new questions through some mill that points the writers at tag-categories and past questions.
I continually find newly given answers that are actually better answers to questions that I have totally lost track of. So I cannot even give the references easily in comments.
At the risk of scaring some folks who thought their insight was novel, this might give serious newcomers some context for their thought, and get them to edit before we have to ask them to.
I think good examples of good questions up front might be a better way of getting good questions than pointing them at suggestions that feel more like rules. (This last may be complete bias. As someone whose fourth and fifth most common references here so far are Wittgenstein and Nietzsche, I find rules fascinating, but have little intention of following them. And I would obviously like more people like me here.)