The art of persuasive discussion

Like most things in life, the art can be broken down to simple guidelines. Rules that are intuitively obvious to the most casual of observers:

1. Be civil and truthful.
2. Decline to reveal what you're not comfortable sharing.
3. But be polite only as far as you can tolerate your own hypocrisy.
4. Call out bullshit in the tone most appropriate to the company.
5. It is OK to let a thought go unexpressed.

or, if you prefer a more pretentious authority, like Philip Dormer Stanhope, 4th Earl Chesterfield

Learn to shrink yourself to the size of the company you are in. Take their tone, whatever it may be, and excel in it if you can; but never pretend to give the tone. A free conversation will no more bear a dictator than a free government will.