This is very abstract, but more concretely, what I mean is that it helps to read about the philosophy/history of science. The canonical recommendation here is Thomas Kuhn's The Structure of Scientific Revolutions [1], but I also strongly recommend watching James Burke's Connections tv series [2] and then watching or reading his The Day the Universe Changed [3] to understand how our entire conception of "reality" or "truth" is so strongly determined by the technology of the time.
Finally, there are lots of "truths" in fields where this is no scientific basis to fall-back on -- politics, art, etc. For these, you have to seek out and find the best elucidators of each field (usually, but not always, books).
[1] http://en.wikipedia.org/wiki/The_Structure_of_Scientific_Rev...
[2] http://en.wikipedia.org/wiki/Connections_%28TV_series%29
[3]