When it’s going to rain, take an umbrella.
If it’s due to be cold, wrap up warm.
If there’s ice on the path, take care!
Sensible advice that many can follow, partly because weather forecasting has got pretty good. More data helps to create more reliable predictions, which helps direct advice for those who need it.
The forecast for vivas, and the advice that follows, can also be viewed similarly, but comes in two parts. First, general advice, because there are general expectations for vivas – the atmosphere, the intentions, the needs, the outcomes, and so on. Vivas happen in certain ways, so it follows there are general preparations to make.
The second part is your unique circumstances. There are things you need to do for the viva, and things you need to do for yourself. Generally, you might need to read your thesis, learn a little about the process and your examiners, and reflect on how you’ve got this far. But specifically, for yourself, you might have to write a particular summary, or have a mock viva, or wear something that helps you to feel confident.
In both cases, there is lots of data to help you forecast: information about vivas and information about yourself. It’s up to you to interpret that data, see where it leads you, and act accordingly.
What’s your viva equivalent of taking an umbrella?