I was just asked for some advice on PhD viva, so have turned the email into a blog post.
They often start by asking you to place your work into context of existing literature and summarise your main findings in 5-10 minutes, so have your summary ready.
The main prep I did was to read my thesis as many times as I could bear to. Don’t worry about errors you find (I found a glaring typo on the 2nd line of the abstract!), they don’t know your work anywhere near as well as you do so they won’t necessarily notice the same things. Doesn’t hurt to think of answers to any errors you do find though.
I had 3 examiners, they had different areas of specialty so generally one of them would lead on one area and the others would chip in as and when they had something to say. It is really more of a discussion than a grilling though, the best thing you can do is to go in with a relaxed frame of mine. There is no telling what kind of questions they will ask you (my mock was totally different from my main viva), so don’t freak out if you don’t know the answer, just say you don’t know or ask them to clarify.
Mine started with the intro (not always the case, apparently some examiners like to mix it up), nothing too hard in there, mostly just checking your wrote it. Prepare to justify yourself in the methods over things like media selection (especially if you have some old school microbiologists like I did) and assay selection. Results are obviously the crux of the matter, hard to say what to expect here because I don’t know anything about your thesis, but mine was focussed on the first 2 of my 4 chapters, probably because those were the ones that were in the examiners areas of interest. So that is the best advice, check out what kind of work they do and try and guess which chapters they will be most interested in. Look what kind of methods they use and justify why you used the one you did rather than their one of choice.
The questions were mostly toward the basic end of the spectrum, more specialised in the areas of examiners expertise, but if that isn’t the main area of your work then don’t worry too much. For example, my worst moment was the proteomics specialist ripping the shit out of my proteomics chapter with high level questions, but I had 3 other chapters of different stuff so was not too worried.
In terms of new articles, I only discussed ones that were directly relevant to my work, they were happy with that. As long as you seem to be aware of other organisms and fields outside your own, I think that is fine.
They don’t feel like they have done their jobs unless they make you sweat a bit at one point, don’t worry when it happens (as long as it is only once or twice, not everything!), just say ‘that is a very good point’ and wait for them to say something else.
Doing a mock viva is a good idea.
You know way more about your subject than it feels like, so don’t worry!