From an undated but late Victorian self-help / etiquette book called Don't: A Manual of Mistakes and Improprieties more or less prevalent in Conduct & Speech (Ward, Lock, London circa 1900). The author is noted as 'Censor' and some of the advice still holds, e.g. bores, exaggeration etc., as for the 'scandals of the hour' - it would now be considered very dull NOT to be able to discuss them...more to follow.
DON'T talk over-loud, trying to monopolise the conversation.
DON'T talk to one person across another.
DON'T whisper in company. If what you have to say cannot be spoken aloud, reserve it for a suitable occasion.
DON'T talk about yourself or your affairs. If you wish to be popular, talk to people about what interests them, not what interests you.
DON'T talk in a social circle to one person of the company about matters that solely concern him and yourself, or which you and he alone understand.
DON'T talk about your maladies, or about your afflictions of any kind. Complaining people are pronounced on all hands great bores.
DON'T talk about people who are unknown to those present.
DON'T be witty at another's expense; DON'T ridicule anyone; DON'T infringe in any way the harmony of the company.
DON'T repeat the scandals and malicious rumours of the hour.
DON'T discuss equivocal people, nor broach topics of questionable propriety.
DON'T dwell on the beauty of women not present; on the splendour of other people's houses; on the success of other people's entertainments; on the superiority of anybody. Excessive praise of people or things elsewhere implies discontent with people or things present.
DON'T introduce religious or political topics.