Forbes magazine offers us examples of things we should not say at work.  See Forbes article. Topics to avoid include sex, religion and politics, of course.  These are topics that can get folks riled up easily.  A thoughtless comment, seemingly harmless banter can linger.  According to one survey, only one-third of senior managers felt comfortable discussing their political views with colleagues. One lady remembers when she slipped up.  The boss, a senior manager, proudly announced at a meeting that he had voted for the Colonel, referring to Oliver North running for the Senate in Virginia. Without thinking, Alison Risso responded, "I pray to God you mean the one who sells chickens." Ms. Risso did not last long at that job.  

Beware of off-color jokes.  Be very wary of humor based on ethnic or gender stereotypes.  Never, ever discuss or "joke" about committing any sort of violence at work.  Do not discuss in any great detail operations, surgeries, or treatments.  

Don’t say "that’s not my department."  if you are not willing to invest five minutes into an issue for your boss or co-worker, then you have demonstrated your lack if interest in your job. 

Workplace morale requires some light topics. Workplace communication is greased by easy conversations and harmless banter.  I remember the Lieutenant-Colonel who insisted that lower ranking persons stand at parade rest in his office, with no hands in their pockets. He would not allow his staff, officer or non-commissioned officers, to sit in his office when providing important information.  You know that particular Lieutenant-Colonel was often out of the loop on critical developments in our work place.

Or, as the Forbes article explains, one new CEO had trouble getting his employees to follow his directions. When the consultant met with him, he told her up front that he did not care what his employees thought of him, so long as they did what he told them.  The consultant and author ("Shut Up and Say Something") recommends don’t tell employees "just do it" or "you don’t know what you are talking about."  Even in the Army, or perhaps especially in the Army, that does not work.