How to greet/say goodbye to people.
If you LIKE them (very rare): Give them an emotionless but polite “hello” but do not otherwise pursue conversation.
If you are APATHETIC/NEUTRAL towards them: Give them some sort of FAINT acknowledgement (perhaps) if you’re in the mood for it. Otherwise, skip it.
If you DISLIKE them (for no reason other than you’re a prick): Return their greeting/farewell with COMPLETE ignorance OR (even better) just look up slightly, stare at them coldly, and then look back down. Best when done several dozen (hundred?) times to reinforce the effect.
Whatever the case may be, try to avoid conversation. Because then they’ll probably think this:
http://www.youtube.com/watch?v=5hfYJsQAhl0
10/16/16: FAIR USE: CRITICISM – A good bit from a really bad movie. (housekeeping)