The text is written by Steven Ray Wilson.
I have administered a bunch of PhD. defenses at the University of Oslo, and would here like to share some thoughts on what you can do to make your PhD defense go as smoothly as possible. This is a short guide for Ph.D. students who have had their work found worthy of defending, and a date has been set for the Big Day.
1. The 24 hours Before Your Defense: Be a Pro, Get some Rest
Your Big Day can be quite tiring, so make sure that the 24 hours before are spent on final minor polishes to your talks, and relaxing as much as you can. Get a good night's sleep!
Tip #1: If you are planning on having a party the next day, try to delegate chores to your friends, family, colleagues, etc. After all, everybody wants you to be fresh and professional for your Big Day, and not sleep deprived because you were cooking all night.
Tip #2: The defense is a formal event, so you should avoid "everyday clothing". But wear clothes that you are comfortable in. Breathing is needed for becoming a PhD!
Tip #3: You will most likely be introduced to the opponents in the morning. They would certainly appreciate if you thanked them for taking on the task of opponent.
Tip #4: Make sure that the computer, projector, etc. is working, at least an hour before showtime. Make sure you know who to call if there is a technical issue.
2. The Trial Lecture: A Step Away From Your Comfort Zone
About two weeks before the Big Day, you will be given a topic for your trial lecture. You can expect the topic to be somewhat related to what you are doing, but a bit outside of your comfort zone. For instance, if your PhD work is on "Skateboarding in the 1990s", a trial lecture topic could be on "Snowboarding in the 1990s". Related, but not too similar.
Your trial lecture is meant to test your abilities in collecting information on a topic, and communicating this clearly in a talk. It is also excellent practice for your future jobs, which will guaranteed not be exactly what you did in your PhD.
Tip #1: Look at all the words in the assigned topic, and make sure you address them all in the talk. For example, if you have been given the topic "Snowboarding in the 1990s", make sure that you talk not just about snowboarding in general, but about the sport in the 1990s. You want to make sure you are answering exactly what is asked of you.
Tip #2: If the title is very broad, it may be wise to proactively focus your talk. For example, "Snowboarding in the 1990s" roams both downhill and vertical snowboarding, but the latter has by far the most followers, development, and literature. Therefore, you may choose to put weight on vertical. But: In your talk, state that you are making some choices, and why!
Tip #3: Avoid tweaking the trial lecture over to your specialty. The intention of the trial lecture is to be independent of the rest of the day. You can mention similarities to your PhD study, but avoid ending up with a lecture which really turns out to be about skateboarding, so to speak. You want to show a versatility in your approach to scientific literature!
Tip #4: There have been a few times that trial lectures I have administrated have nearly been found to be unsatisfactory. The reason has been that the lecture was too short. The lecture is for 45 minutes. For the love of God: Make sure you have enough slides to fill 45 minutes! If your talk is clearly less than 40 minutes, you are in danger. Consider having some additional "emergency" slides that you can discuss at the end if needed. If you don't need them, bypass them with the shortcut button which leads you to the last, concluding slide. This will make the lecture less of a heart attack for you, the audience, your supervisors, and the opponents.
After the trial lecture, get something to eat. This is not the time to diet; sodas and chocolate are fully permitted, you need fuel for the Main Event!
3. The Defense: Know Your Basics, and Discuss!
The Main Event starts with your 30-minute overview of your work. It is common to try and explain the work as basically as possible. Try to have a few slides at the start and end that can be comprehensible to non-experts, like non-academic family members. It can be a nice touch to thank those who have helped you along the way at the end of your talk.
After the first opponent has given his opening remarks about the work, your discussion begins.
Tip #1: Ensure that you have beforehand gone through the basics of your work and field. Opponents may start with "softball" questions that are from basic courses. But sometimes these can be surprisingly tricky to answer! It does not hurt to skim through a few elementary books to refresh your memory.
Tip #2: If you get stuck on a question, that is quite ok. It is actually a bit of the point of the whole show! Try to resonate, and ask the opponent for more information, if needed. Don't try to talk your way out of the topic, this can irritate the opponent.
Tip #3: If the opponent criticizes a part of your work, and you disagree: Try to "fight back"! You might be right, and he/she might be wrong. Most opponents would love to "lose" a discussion, as this would be a sign of maturity and comprehension with the candidate. But at all costs, avoid being arrogant.
Tip #4: Save energy for the 2nd opponent. He/she may be even trickier than the first. You can also ask to use the restroom between opponents.
Tip #5: Towards the end: You may be asked questions that the opponent does not know the answer to. This can be an opportunity to have more philosophical discussions. Finally, you might be asked what you liked most about your work, what does the work mean for science, etc., so think through what your work means in the Big Picture.
I cannot guarantee that all of these tips will apply to exactly your Big Day, but I hope that some of these can help you.
So good luck. You have come very, very far.
If this day is still far away, you might be more interested in these tips: How to survive the start of your PhD!