The girl from Ipanema gives us a first-hand look at the survival skills of a post-doc:

It basically involves very very thorough reading of the literature (aim for breadth, rather than depth), striving to stay up to speed on current work (possible competitors, collaborators, ones that tried it and failed etc.) and then the ability to assimilate all the varied reading and posit your question/hypothesis/goals in this context. You must not only be able to evaluate factual loopholes in the science of what you aim to do, but also technical loopholes that will point to how difficult/easy/doable what you’re planning to do is.