Working for a large corporation in an office building with ~200 people, there are some interesting dynamics that take place. The specific interaction I would like to focus on today is that of the hallway encounter.
I would estimate that I am out in the hallways 8-10 times throughout my day, either going to the bathroom, getting hot chocolate, or visiting other people at work. In my path, I usually encounter one of three types of people, and what follows is the rules necessary when interacting with them:
1) Stranger -- someone who I have never before had a conversation with and/or you don't even know their name. Upon approach, no verbal or physical contact is initiated, but a smile or head nod is acceptable. If verbal contact is initiated by Stranger, treat as Acquaintance.
2) Acquaintance -- someone who you have been introduced to and have had a conversation with before. Verbal contact is initiated, and consists usually of a "How are you doing?" or a "Hello". Note that when a question is asked, such as "How are you?", no response is expected. There is no hesitation in walking pace, and the dialog should be brief. If other party does not respond to your verbal contact, they may in future be treated as Stranger.
3) Colleague -- someone who you have had many conversations with. Physical contact is initiated by slowing down the walking pace. If the other party also slows down, you stop and begin a conversation. If the other party does not stop, you must increase pace to normal walking pace and treat Colleague as Acquaintance. Conversations (when both parties stop) must last a minimum of 90 seconds. Upon ending of conversation, parties salute each other by saying "See you later" or something similar, knowing their paths will likely cross soon.
Any questions?