What parts of the accounts seem most reliable, and what criteria can be used to sort out degrees of accuracy?

The idea needs to be tested for it to be scientifically reliable. First, a hypothesis has to be drawn up. A simple explanation for the word "hypothesis" is an educated guess.  The scientist makes an educated guess in answer to a problem. He then sets about proving or disproving the hypothesis. This is done by setting up related scientific experiments. For the theory to be scientifically proved, the experiments need to be set up in such a way that the results are measurable.