One of the first things that the professor in my cryptography class told us students was that pretty much everything we know or believe is ultimatively based on trust. There's hardly anything that we have actually verified.
There's no definite solution to this dilemma, in the end, you can never know for sure. In the case of opposing models/explanations/theories, I believe the best practical solution is to hear all sides and simply consider what explanation you find most plausible.
In the case of evolution vs. "god created earth 6000 years ago" for example, I believe evolution simply offers a much better model, as it offers a measurable and plausible explanation for many things that you can discover in nature.







