Also I find looking up the author and everything can help
yup, loads of things, the date of the source as well in relation to the event.
bottom line, you can only really even trust your senses most of the time, because they will trick you some of the time...
HiQ, i would suggest looking into Epistemology, and then maybe objective thought and empirical knowledge. (this is not meant to deny subjective thought or faith in general, just that in terms of validating sources as a science, one side is more relevant than the other)