This is a critical question if you are in a position to be contemplating doing one (normally as a result of a subject you are interested in at University). The first question to answer is do you need to do a PhD for the career you are considering? My advice is to talk to as many people as you possibly can about this and gain some practical experience of your field.
If you are considering doing a PhD in order to become a researcher of some sorts remember research is hard, really hard. You are also liable of having to move cities and sometimes countries in order to work in a field you are interested in. Academic institutions are quick to tell you the benefits of a scientific career and indeed encourage high numbers of students (in my opinion often too many) to do a PhD without highlighting draw backs such as spending up to ten years on fixed term contracts, in other words your contract can end and you may need to move cities in order to find work. This can prove hard if you ever want to own your own house or have a family. It may seem a long way off now but it will creep up on you. These are things I do not remember the University or careers service mentioning.
Regardless, well largely oblivious of these things, I took the plunge and decided to do one.
Most of the logic that went it to making this decision was in hindsight fundamentally flawed but in my case not necessarily in a bad way.
My thought process went something along the lines;
1. Overall, even given the stress of exams, I enjoyed learning during my degree and enjoyed my subject I think I want to do more.
2. I am not entirely sure of the career path I would like to take and surely it wouldn’t hurt to do a PhD and surely I must be more employable as a result.
I had some previous research experience on a summer school, so had some basic research experience but I didn’t like the idea of paying for a Masters (there are few funded masters opportunities in any branch of research). I thought therefore I would try and get a job as a research technician to gain some further practical experience. Fortunately I was able to secure a position (something that I am not sure I would be able to now) and I am still truly grateful of this experience and the continued advice I receive from my previous inspirational boss.
This was crucial as it really gave me a flavor of what it physically entails to do research whilst looking for a suitable PhD position. Unfortunately with funding cuts to research budgets you see less and less research technician/assistant positions advertised. A masters degree has now almost become a requisite for entry into most PhD programs. This is most likely the consequence of the increasing numbers of graduates (there was around 100 people on my undergraduate degree and at my current university there are around 260 on a comparable course) often with little or no practical research experience.
Just like research, do your research on the area or areas you are thinking of working in as a starting point and then look to gain practical experience in this area.
I think as much as experience and exposure to the laboratory environment is crucial if you are to make an informed decision. Most people, at least these days, would not move to another country without visiting it (at least I hope so) as you can’t be sure you can see yourself fitting there. The same is true for research, you might have loved the theory but can you put up with the tedium (at times) of running experiments. Although research technician positions have become rarer, many Universities offer paid (competitive) summer schemes for undergraduates to gain research experience and provide an ideal platform to gain research experience and strongly encourage anyone considering a career in research to apply. Ideally, at least in the UK you want to contact people you are interested in working with just after Christmas. The deadlines for project proposals are around March each year. Don’t worry you wont have to come up with a proposal but if you can help come up with one I think most potential supervisors would be very impressed although it obviously has to align with their interests/area of expertise.
In terms of enjoying my subject, overall given the drawbacks I still love it, you tend to call it your field strangely enough and not subject. I think you have to love to work, almost to the point of obsession, as honestly you are up against people like this who are competing for the same positions as you the higher up the academic ladder you attempt to scale.
As for being more employable, having a PhD does not necessarily make you more employable contrary to what any of your friends/general public may think. You have a PhD you must be sooo clever (you actually end up knowing a lot about very little) therefore it must be easy for you to get a job. I took some time out after my PhD to travel and upon returning to the UK in the height of a recession struggled to get any form of work despite my best efforts, I applied for pretty much temporary job imaginable and worked as a accommodation inspector, exam scribe and was a taste tester for a supermarket, not as glamorous or tasty as it sounds. Your PhD is great in that it makes you relatively specialized, but it also terrible in that it can make you, at least seem, relatively specialized. So when there is demand for these skills or this area then you have wide ranging choice. However when there is not, or these skills are in abundance you do not have that choice. It should be noted doing a PhD gives you many transferable skills, time management, creativity, problem solving (almost constantly if you do life science research) and a broad experience of science. When applying for jobs that do not require a PhD you really need to show that you understand the role you are applying for and how your PhD skills will enhance your function in whatever role your are applying for.
In terms of would I do a PhD again, my answer shortly after finishing would no, never again, just because of the effort required to consolidate three years of research into a thesis. Having had time to mellow with age, I most definitely would do it again. The joy of making your own discoveries is one of the greatest feelings and contributing to human knowledge is really satisfying. The thought that your research may just benefit someone someday is the cherry on top of the cake. Life is a journey, doing a PhD will enrich it both from the people the meet and the experiences you will discover and rather than seeing moving as daunting I see it as challange and an opprtunity to live and work somewhere new.
Happy looking for your perfect PhD.