Behaving As Expected
PhD candidates can get a sense of what to expect for their viva from reading their institution’s regulations, learning about general viva experiences and asking about recent vivas in their department.
Together these create expectations.
Some expectations will be really clear, like knowing the people who will be examining. Others will cover a range of possibilities, like expecting the viva to be longer than two hours. Some aspects may be unknown but a candidate can still get a sense of the situation: you might not know the first question but will still have an idea of what examiners typically ask.
Viva expectations prompt behaviour. This sort of thing will happen so I will do this to be ready.
Consider what you know about the viva and how that can help you as you prepare.