I am forced to admit that upon first thought, all that came to mind regarding elevator mores and social standards I have gleaned from my own personal experience: I have best learned what is and is not acceptable in elevators by doing the unacceptable thing and getting negative response. Generally, the best policy regarding the behavior of elevator patrons is to respect each other’s personal space and remain silent.
For example, the fastest way to break an accepted social more in an elevator is to stand as close to other people as possible if there is ample space for everyone to keep a comfortable distance. Walking into an elevator car occupied by only one other person and standing very close to them infringes on their personal space and generally makes them feel very uneasy; it is for this reason that there is an unspoken rule that personal space, especially in American society, is very important.
In elevators, it is generally a good idea to remain relatively quiet. The fastest way to annoy others, especially in an enclosed area, is to talk incessantly about nothing in particular or act at all out of the ordinary (i.e.: feign mental illness, talk to oneself, make rude noises, twitch, etc.) Perhaps this, “Do not speak, do not move, do not even breathe loudly” general ‘suggestion’ is gleaned from the fact that people in general have a distrust of strangers and want to remain anonymous and invisible in situations with which they are not familiar.
Lastly, behavior in elevators can be largely dictated by the personal appearances of the people in it, and their responses to their fellow patrons. For example, if a teenager garbed in black with a ring through his nose and a tattoo that says “Krush” gets onto an elevator, a double-breasted-suited businessman may fidget more vigorously and profusely than he would if an elderly lady with a potted geranium boarded the same elevator car.