Scientific Method, Socratic Discourses. Debate everything until you're blue in the face, examine every precept or "given truth", question every fundament.

True from false you can divine with the above, but only within the constraints of what we know and can know - this is the epistemological route.

Right from wrong is an entirely different topic, and is an ethical and moral question. A good starting point for considering the very definition of "right" and "wrong" might be to read or read about Kant, Plato, and Aristotle - but ultimately what's "right" or "wrong" derives from the very subjective societal norms of whatever cultural context you find yourself within.

There's essentially nothing which is considered universally right, or universally wrong - you get to figure this one out for yourself.