A useful question to ask yourself before you speak is how you would respond if you were in the other person’s position. This will prevent you from saying something you might think is polite but actually leaves the other party floundering.
Self-deprecation is a dangerous area. At a training event I attended recently, one of the speakers opened by saying, “And now, I’m afraid, you’ve got me for an hour. Sorry about that.” Well, honestly! If you really mean this, your apology is inadequate: if you’re not up to the job, you shouldn’t be doing it. But most people who talk like this don’t really mean it; in fact, quite the opposite. Faux modesty of this sort is transparent – and it’s irritating, not least because the listeners don’t know how to respond. At best, this kind of comment comes across as needy, and it’s not the audience’s responsibility to meet your needs: that boot is on the other foot.
At an evening where authors were discussing their books, someone from the audience was making a contribution and wanted to address herself to one of the authors in particular. In her memoirs, the writer had always referred to herself by the pet name her family used, while the person chairing the event had introduced her by her full, official name. “I don’t know what to call you,” said this audience member, to which the author replied, “You can call me whatever you like.” Needless to say, this didn’t help. It was uncomfortable because, while on the surface it’s giving friendly permission, in fact a remark like this just heaps confusion on someone who is already unsure.
When this type of thing happens, it’s usually because the speaker is not properly grounded and is more concerned with making a good impression than with what is genuinely in the service of the listener. Putting yourself in the other person’s position is a good way to assess for whose benefit you’re speaking and to avoid any clunking mismatches between the effect you want and the effect you actually have.