You will find a lot of information on "things NOT to say/do at the office" on the internet, including advice against discussing politics or religion in any professional setting. In our seminars and coaching sessions on professional and personal image building & management - We make it a point not to repeat any information that is over circulated, unless they serve the purpose of a quick reminder, as we all need from time to time. Here are some things I would strongly advise against saying/doing at work, or even in social interactions, to avoid any awkwardness and discomfort:
1) "Oh you look so TIRED! Are you OK??"
It most likely stems from kind intentions, but that will either embarrass the other party or sadden them. It can be misconstrued as: "You look haggard/bad, something is WRONG with you".
2) "Why are you SO DRESSED UP?"
This can be taken as: "You should not look THIS NICE".
3) "Don't you feel warm/Don't you feel cold in that outfit?"
Everyone's body, preference and tolerance are different. Don't make others feel uncomfortable by pushing YOUR standards on them.
4) "I see that you have gone shopping at lunch! What do you have there (in that bag)"
What if that person has just gone to get medication from a pharmacy? Or they have purchased something that may be a bit embarrassing to share?
5) Staring at your colleagues' computer screen as you talk to them
This is basic respect, but many seem to make this mistake at work.
6) Peeking into your colleagues' offices as you pass by
Unless you are genuinely seeking for eye contact to greet them, it is a little rude to be doing so.
7) Having LONG social conversations with colleagues at work, not taking any hints to leave for them to get back to work
Be more thoughtful and sensitive to others, no one likes a chatterbox at work.
8) Talking/Laughing loudly
I know some may argue that you are "being yourself" but anything that disturbs others at work should be minimized.
9) Setting your phone volume to high/max
This is just plain RUDE.
10) Marching into someone's cubicle or office without at least a slight knock
Again, we all should provide a discreet "warning" before we approach the work space of someone so no one gets startled. You also provide a brief moment for them to compose themselves.