Edit/add: due to a misread I answered on 'how to detect unknown unknowns'

This post also makes me wonder if there are any (possible, not necessarily already discovered) generalized strategies for detecting unknown knowns

Maybe not a real strategy. Read what interesting and/or bright people write, That covers a lot and help with uncovering things that some others already know. For daily behavior you might check the quirkology book or more of the writings of Richard Wiseman. To really discover unknown unknowns, like from Eliezers famous question on what strange thing an AI might tell us, I don't see a super general way. Being curious still goes a long way. Thats how I ended up with my current collection of non-standard habits and ideas.