I've added all the links mentioned so far, to Git/Tips#See also.
Hopefully you folk who understand the contents, can compile the best bits into 1 or 2 locations (either those existing locations, or new pages). E.g. a "complete newcomers guide" (suitable for someone who has basic "editing spelling errors in github" level experience, but has managed to get mediawiki (and etc) installed locally).
Or something along those lines. :-)