Here are some things I wish I knew at the start of my PhD. Better routines and knowing when to stop a project would have made me more effective, so I hope this helps others avoid similar mistakes.

For background, I’ve just finished a PhD at the intersection of Bayesian statistics and infectious disease epidemiology, based at the University of Cambridge, UK.

Be cautious about advice

Before I begin, a warning. PhD experiences vary widely, influenced by numerous factors such as country, university, supervisor, field, and your unique personality and work style. Country especially: American and UK PhDs are such different experiences they should be considered different things. Therefore, take all advice, including mine, with a large grain of salt. Don’t be surprised if you hear conflicting advice or experiences from different people, use the parts that work for you.

Focus on the advice relevant to you. For example, if you have the same supervisor as someone else, seek tips on effective interaction with them. If you're in the same department, identify who is valuable to talk to. Relatedly, seek advice from people sharing your supervisor / department / field where possible.

Along those lines, here is some other advice I think is worth reading.

• Adam Howes: I basically agree with him on everything. The one point of disagreement is that I’m not sure you need to be thinking as strategically as he says with your research, especially in your first year.
• eca (pseudonymous): I disagree with this for the same reasons as Adam Gleave. Like him, the academics I worked with didn’t respond strongly to incentives, although I haven’t been in industry to make that comparison.
• Sandy Hickson: focuses on the process of choosing / getting a PhD. While going as deep as him on choice is probably good, the vast majority of people don’t (I met my supervisor once, for 30 mins, although I was definitely making a choice with too little information). I was a non-international student and applied to an already-funded project, so I can’t comment on that part.

Choosing a PhD

Consider your PhD choice as seriously as a job decision. Evaluate the "boss" (supervisor) and "team" (research group) dynamics. Evaluate the culture within the research group. How collaborative is it, both within the group and externally? Understand your potential supervisor's management style and the level of attention they will provide. Often, a postdoc will supervise your work instead of your main supervisor. Hands-on supervisors provide more guidance but less freedom. This is probably the most crucial part of your choice. The best people to talk to will be recent students of your potential supervisor.

You might want to consider what you’re hoping to get out of the PhD. One extreme is people who just want the credential (e.g. they want a job that requires a PhD but the details don’t matter). In that case, choose a programme where students reliably finish on time. Your goals might not align with your supervisor's, so be prepared to assert your needs. The other extreme is those that are sure they want to pursue a career in academic research afterwards. Then, getting good publication(s) is very important; for fields where author order matters (e.g. life sciences) these should be with you as first author. Assess where your potential supervisor, and their recent students, have published; often, one publication in a top journal is worth multiple in lower journals. Most people fall somewhere between these extremes, and aren’t sure what they want to pursue post-PhD. Consider different aspects of your potential projects and find a balance; remember, no project is perfect.

The key part of a PhD is gaining knowledge and skills; ideally, transferable ones. This is far more important than the impact or usefulness of what your research is within your PhD (although that’s good too). Therefore, being in the right general area using the right methods is more important than the specific project. The skills, connections, and ideas you gain will open doors later.

Remember, your research direction might evolve in unexpected ways.

Doing a PhD

A regular work routine helps you stay organised and manage time effectively. Whether you prefer traditional 9-to-5 hours or a schedule that suits your lifestyle, having a consistent routine will also help you maintain a healthy work-life balance.

Setting clear goals and getting your supervisor's support is crucial for a successful PhD. Don't be afraid to challenge your supervisor's ideas if necessary, but do so respectfully and thoughtfully. Changing supervisors can be disruptive, so it's important to weigh the pros and cons carefully before making a decision.

Be wary of the never-ending nature of research projects. It's important to recognize that there will always be limitations and potential extensions to your work. If you're starting to lose motivation, consider wrapping up your current work into a coherent piece, such as a paper or thesis chapter, before moving on. If your supervisor disagrees with your assessment of the project's completion, ask if you can take some time to write up what you have. It's often easier to discuss what's missing and whether there's enough material for a paper once it's in draft form.

During your PhD, you have a lot of freedom. Use it to explore side projects like collaborative research, outreach, or internships. These experiences can help you determine your career path after graduation. While the number of options can be overwhelming, try a few different things to find what interests you the most. As David Allen said, "you can do anything you want, but not everything."

If you want to stay in research, start thinking about future research directions early and write them down, you won’t remember them in six months. Identify external collaborators and compare potential projects based on the effort required, impact, your motivation, your comparative advantage in executing them, and how much you’ll learn from them.

PhD days are incredibly unstructured, having two hours of scheduled time per week (a group meeting and a supervision meeting) is common. A particular challenge is the very high proportion of deep work: stuff you can only do with intense focus. It’s often worth just taking an hour or two off for a nap or a walk then going back to something, rather than forcing yourself to stare at a screen without making progress.

Find a working style that suits you. For me that was prioritising the most important task each morning and then doing something I’m more excited by, but not necessarily that important, in the afternoon. This approach can enhance productivity and maintain motivation. I strongly recommend maintaining a list of useful or interesting things that would be helpful to do or read, but aren’t necessarily that important.

Writing your thesis

Writing a thesis is daunting; I struggled, and most people do. Everyone tells you to complete projects and draft papers or chapters as you go; this is great advice few people follow-through on. Maybe you can buck that trend.

Allow more time than you think for writing. Writing a chapter from scratch is hard, each one took me around two weeks. You’ll then have a bunch of comments to address and revisions to make. Starting from a pre-existing paper, it would take me around a week to write the chapter and there'd be far fewer issues with it. It’s better to have a draft early then add stuff to it than to overrun. See also: earlier comments about never-ending research.

Sitting your viva

The viva (or defence) is daunting, but doesn’t influence much: the majority of your corrections will be decided beforehand. However, your answers during the viva may reduce the extent of them, for example you might be able to convince them that something just needs to be explained better and isn’t wrong.

Preparation quickly hits diminishing returns. I spent four or five days in the week beforehand preparing and this felt about right; remember to be well-rested through this period too. I recommend focusing on the details, making sure you are on top of the details (e.g. definitions of technical concepts), and why your arguments are correct (e.g. implicit steps made between steps). Rereading your thesis with fresh eyes can help you find mistakes and identify the most important parts. Other useful activities include going over key papers you have cited or your examiners were involved in, and summarising each chapter and the entire thesis into one page each. This exercise can help you get out of the weeds of the details and think about the big picture.

Depending on your examiner, the types of questions you may be asked could vary greatly, so it is impossible to prepare for all of them, and hard to predict what they’ll be. Your supervisor may be able to give you clues about what each examiner will focus on, but it is also important to be prepared for anything. You’ll normally be asked to give a short summary (3-5 mins) of your work at the start. I don’t think this is really examined, it’s just to get you into your flow, but be prepared for it.

On the day of your viva, it is normal to be nervous. Control whatever you can control: make sure the room is set-up correctly, you have everything you need with you (copy of your thesis, any notes, water, etc.), you’ve planned out your time through the day, and you remember to eat and drink.

Finally, remember that they are asking you questions about work you have spent over three years on. There is no one in the world who knows more about this stuff than you do.