@allen_menezes First step is to make sure that the text was written when it claims to have been and by whom it claims to have been.

One might look at manuscript evidence, internal linguistic evidence (anachronistic language can indicate forgeries), whether the dates add up, contemporary references, consistency with known sources.

Once you establish a text is real, meaning it's from the time period/context it claims, it is another matter whether it is accurate on specific information.