Given a claim, consider the question "What would the world look like if this claim were true?" and try to generate ~4-8 independent predictions. Then, look at the world, and check whether these predictions are borne out. If they are, then by Bayes' theorem, you can develop some confidence in the truth of the claim. If the predictions are not borne out, then by Bayes' theorem, you can develop some confidence that the claim is not true.