I'm sorry if this has been asked before, but I've been scrolling through the forums all day (and night) looking for ideas, and I've found *nothing* on the subject. Lots of stuff about fonts, yes... keys, no...

I see many maps with a little corner-set key like we saw in my grade-school geography books.

And I see many with labels directly on the map "Misty Mountains" soaring in huge letters across the mountain range...

And still others have no labels, or lovely little informational sidebars..

How do you know what style of labeling (not font! placement!) to use on any given map?