The Filter^: Persuasion, Conviction, and Convincing

When experts argue, who should you trust? Arnold Kling:

when an economist known for one ideological leaning makes an argument that favors a different persuasion, that in itself should lend credibility to the case
force economists to explain their arguments clearly in layman's terms, and then to evaluate the arguments on their merits. That means you have to know enough about economics to be able to distinguish a compelling economic argument from demagoguery.

Compare credentials. If the advocate of X teaches at Harvard, and the opponent of X teaches at a community college, this raises the probability that X is true. (And yes, this means that all else equal, you should side with Dani Rodrik against me. Fortunately, all else is not equal).
Adjust for social sanction. If X is a popular, crowd-pleasing conclusion, you should expect this to make smart defenders of X more abundant - regardless of the truth of X. You should therefore hold the defenders of such views to higher standards.
Check the bets. If only one side is willing to bet hard cash, that side is probably right.
You don't have to take a side. If you really have no idea who to believe, remain agnostic. In fact, it would be much better for the world if the less-informed practiced Swiss neutrality, leaving the well-informed to guide policy.

I'd emphasise that last point, since I feel that the biggest public policy problem isn't a lack of knowledge, it's an abundance of incorrect knowledge. We'd all be a lot better if we raise the bar of how much we understand an issue before expressing an opinion [cue Jim!]. I'd also add