Dr. Drang informs us of the proper way to refer to keyboard shortcuts on Apple products, as defined in the Apple Style Guide:
Control (⌃), Option (⌥), and Command (⌘) always go in that order. The oddball is the Shift(⇧) key, which sneaks in just in front of Command.
But here’s the thing: I absolutely do not follow this style. It seems completely backward to me, in fact. It’s not “Shift-Command-3”, it’s “Command-Shift-3.” Command is the commander! Command is the monarch of all keys! Command always comes first, in my book.
Of course, your mileage may vary. Apple’s certainly does.
I’ve heard various explanations for the origin of the keyboard shortcut divide between PCs and Macs (Control/Command, Alt/Option). I suspect the root of this debate was not the Mac and Windows, but the behavior of DOS prompts on the Apple II and IBM PC. It’s a funny parallel evolution.
Related: A great column by Christopher Phin about the origin of keyboard shortcuts and symbols. And at Folklore.org, Andy Hertzfeld on the origin of the Command symbol.