I always wonder what to do when I'm walking down a hallway and see someone walking towards me. At what point are you supposed to acknowledge the other person? If I see someone at the other end of the hall, do I wave and yell, "Hello!", or do I pretend that I haven't seen him until we pass each other and nod? It seems a little silly to ignore someone until they're within 3 feet, but then again, if you walk with your head down, it would make sense that you wouldn't see anyone. On the other hand, walking with your head down makes it seem like you're sad or trying to shut out the world.
Maybe what I should do is sprint down the hall as soon as I see anyone -- get right to that "hello" as quickly as possible. Or maybe I should immediately turn around rather than deal with a potential protocol violation.
Speaking of manners, what do you do if you're at a urinal, and someone steps up to the one next to you? Assuming you know the person, do you say hello, strike up a conversation, look at him, compliment his gluteus maximus? Usually I jump back 3 feet in horror and end up peeing all over the wall and myself. There must be a more appropriate approach.