My preparation was to take a complete break from the thesis until a week before the viva and to relax as much as possible. So about 2 months, and this, I think was the most useful thing I did. It meant I was feeling reasonably normal by the viva date.
In the week before I began preparing by answering the following questions from memory, as if I were in an exam:
1. What is the best thing about the thesis?
2. If writing again what would you do differently?
3. What are your research questions?
4. How did you answer them and what are your results?
I then read the thesis as if I were marking it.
Afterwards I sat down, as if I were in an exam again, and answered the same questions. Then I compared the two versions.
I also re-ead anything written by my examiners that related in any way to my thesis. This was a very good move. It meant I was prepared to deal with any faux pas I made in my thesis, which I did, and was forgiven for.
I was very proud of my thesis, although I knew it wasn't perfect. I also had faith that God would take us all the right way, whatever that may have been. I knew my examiners were decent people and that my work was good enough. But I'd have rolled up my sleeves for major corrections if necessary.
I looked forward to it as my big chance to have a really good conversation about my work, which I love.
I gave a brief account of the viva earlier and don't feel I can add much to that other than to say it was not as difficult as I'd expected.