In a conversation today with one of my graduate students, my student observed that there are various folklore tips about applying for postdoctoral positions that are passed down from student to student in an ad hoc fashion, that are not formally recorded in any shareable form. As an example, one tip he received was to look for math postdoctoral positions not just under the "postdoc" listing in Mathjobs, but also under "Assistant Professor" positions, since many postdocs are technically classified under the latter category and not listed as official postdocs.
I myself last applied for postdoc positions almost thirty years ago, so I had little current advice to give on these matters, but I wonder if there already exist some standard venues where these sorts of tips are shared (e.g., academia stackexchange), and if not, whether it might make sense to try to create one. I'd be interested to know of any efforts in this area (if nothing else, it would be an obvious additional set of links to add to my career advice pages).