For strings that are meant for human consumption, use double quotes, otherwise use single quotes.
This is super practical when looking strings meant for translation, end-user formatting, and such.
I'm fairly sure that single quotes are much more common in the UK in literature, though, so this only feels like it makes sense to NA and AU speakers.
It's just that the primary/secondary role is reversed. (This is also reflected in which one you have to hold Shift for on a computer keyboard.)
A bigger issue IME is languages (mostly of the C family) where single-quoting is for character literals.
Also in Smalltalk comments are double-quoted, but that's a pretty rare language to encounter.