Listen primarily to the experts. People who have experience, knowledge, or skill in the area. But please don’t confuse a fancy title or big salary with expertise.
Assumptions? (when trying to challenge them)
Listen closely to the non-experts. The experts are often so used to the status quo it becomes invisible to them. The lay person sometimes has the objectivity and distance that allows them to see that the emperor isn’t wearing any clothes.
Listen to anyone who has them. Real facts are indisputable. It doesn’t matter who provides them, if we can establish it as a fact, the messenger doesn’t matter.