"Don't be gullible" itself has gotchas. If I adjust my skepticism-meter too far upward, then manufactured controversy can seem like real controversy to me -- this fact was used by tobacco companies in the 1960's to sway public opinion and continues to be used today by many other groups. Just because some seemingly-smart people seem to be having a debate about a subject does not mean that the truth is beyond your understanding.

I think the better advice would be "There is no easy path to find the truth." That is, there is no formula or template you can always follow to find the truth. Finding the truth requires continuously challenging your beliefs and questioning authority.