The main trick is to turn "facts" that exist in your head or possibly in a program's address space into something more concrete/searchable/discoverable, like a

The main trick is to turn "facts" that exist in your head or possibly in a program's address space into something more concrete/searchable/discoverable, like a log line, source comment, manual entry, etc. Otherwise, your database of 'facts' and 'values' will inevitably become out of date if you try to maintain it out of band.