I'll second the suggestion of introducing people to overconfidence early on, because (hopefully) it leads to a more questioning mindset.

I would note that the otherwise-awesome Adventures in Cognitive Biases' calibration is heavily geared towards a particular geographic demographic, and that several of my peers that I've introduced this to were a little off-put by it, so consider encouraging them to stick through the calibration into the more meaty subject matter of the Adventure itself.