It may seem like an odd thing to post about, but I’ve been asked about the topic many times before by PhD candidates!
“Is there anything I mustn’t say or do in the viva???”
I don’t think there’s a real danger of being impolite in the viva. You don’t need to look out for anything that wouldn’t occur to you ordinarily about watching what you say, or behaving improperly.
- Try not to swear maybe? (unless curse words and their origins are the topic for your research!)
- Don’t insult your examiners? (hopefully obvious!)
- Don’t be arrogant?
There’s a little ray of worry in the last one. There is a difference between confidence in your work and arrogance at being right. There could be difficulty in balancing talking about the rightness of what you’ve done, as you see it, against questions about alternatives or being sure. That could be tricky. But it doesn’t mean that it should be avoided or obsessed over either.
Talk about alternatives before the viva, in preparation for perhaps needing to talk about it in the viva. Get more comfortable in the trickier parts of your methods and results, then you won’t have to worry about saying the wrong thing.