When I crave meat, I need protein/fat rather than carbohydrates (which is probably a good 80-90% of what I normally consume to be honest; my diet is incredibly bread-rich). And today, I got a craving for fruit (specifically, an apple), which could be for any number of things, I looked it up but can't list them all off the top of my head. Still, when I looked at them, my thought was, "yep, that seems accurate".
It also tends to be a good tiredness indicator, albeit one I consistently ignore. When it says I need to sleep, I should be sleeping, so I'm going to go honor its request.