Hmm... I'm pretty random really. If the door to the room is open, I'll take one to where I dont' think people outside can see me. I just don't like the idea of someone watching me take a leak. I also will go to the one that was flushed since its last use. Oh! If there are Urinal Walls, then I just pick whatever. My Campus has Urinal walls.. Damn its great! Is it so hard to install a few panes of metal along the walls?
As for the toilet? First I look for one that is not in use.. Then I look for a clean one. When found, I do my duty to mother nature.
