If you ask me, there is just one: you produce creative work creatively. Do that and you’re creative, QED. But when you’re looking at a particular office space, there are things you can tell immediately.
Such as this: if there are big, wall-sized decorations with words like “Imagination” then there will be creative people consciously ignoring them. That’s what non-creative people think these offices need and the real creatives are the ones who wouldn’t be seen dead being motivated by that.