Consider starting small, with short, clear and engaging examples, like the Newcomb's problem, the PD or the Trolley problem, or the Milgram or Stanford experiments
Newcomb and Trolley problems are too removed from the real world to be useful topics for an introductory class, and I'd say the others are too advanced for an introductory class. All of them are controversial enough that you can't simply say, this is the right answer and all other answers are wrong.
Thinking aloud about how I might go about it (but without ever having done so) I wouldn't start with biases. I'd start on the positive topics of the truth being out there and what you must do to discover it. The virtues of rationality, with the vices (biases, error) introduced to illustrate how people go wrong. The 2,4,6 problem is about the right level of example to use, rather than exotic decision theory.
I'd start on the positive topics of the truth being out there and what you must do to discover it.
Yeah, I thought about it, but then my personal ontology does not rely on the concept of objective truth, so I've been reluctant to suggest it. It is easy to imagine that postulating objective truth would likely devolve into a discussion of logical positivism and its issues, which is not what the OP wants.
I'm afraid I haven't properly designed the Muggles Studies course I introduced at my local Harry Potter fan club. Last Sunday we finally had our second class (after wasted months of insistence and delays), and I introduced some very basic descriptions of common biases, while of course emphasizing the need to detect them in ourselves before trying to detect them in other people. At some point, which I didn't completely notice, the discussion changed from an explanation of the attribution bias into a series of multicultural examples in favor of moral relativity. I honestly don't know how that happened, but as more and more attendants voiced their comments, I started to fear someone would irreversibly damage the lessons I was trying to teach. They basically stopped short of calling the scientific method a cultural construct, at which point I'm sure I would have snapped. I don't know what to make of this. Some part of me tries to encourage me and make me put more effort into showing these people the need for more reductionism in their worldview, but another part of me just wants to give them up as hopeless postmodernists. What should I do?