Call me old fashioned, but I learned about child theming mostly from the official WordPress Codex page! These days, probably the better source is the new WordPress Theme Handbook page about Child Themes.
I hadn't really looked at the handbook page before but it seems really good with one small exception. I think the way they include the Parent Theme's styles are old-fashioned and there's a newer best practice.
Since I'm complaining a bit, I have to be productive! Here is a quick set of well-commented files you can use to make a child theme: https://gist.github.com/mrwweb/92b1c15abfe74f0e472c20a9b1591adf
Thanks guys for all the great resources for building child themes! This is such a great group.