If I wish to remember something like a number of specific time or some detail like that I may very quickly write it down on my wrist. I just figure if you scribble a note somewhere else you may forget it or lose it, but having it 'tatooed' onto your body there is extremely small chance of this happening so it makes all the sense roud:
Yes, I do that a lot. I used to drive one of my teachers crazy with this habbit. I do have a notebook, but sometimes it is just quicker to write something on your hands. It's especially handy proud when you read something in a foreign language and want to write down some new words to be looked up later on in a dictionary.
OMG. YES! I so do that. It's the only way I can remember my homework. For some strange reason, I abhor day planners and organization thingies like that. I've tried to use them, but you see, planners and I just don't click. Not. At. All.