How do you know if your gecko is dead or sleeping?

Im pretty sure, you just have to hold him for awhile. i pet mine on the head while he lies in my hand, and when i stop, and he doesnt look around, i figure he must be sleeping...or i rub overtop of his eye (where his eyelid WOULD start) and he doesnt stick them in his head. the question would be sooooo much easier to figure out if they had eyelids lol :(