I liked doing research -- I'd started as an undergraduate and wanted to do more. And I wanted to learn more quantum mechanics and apply it to models to understand some (approaching...) real world problems. I liked the place, the research and the atmosphere and fellow graduate students. I went straight after undergraduate, age 22. Finished just over a year ago. I think about the only reason to go to grad school is that you like doing research and/or learning the subject to greater depths whilst on the front lines, worry about and performing the nitty-gritty side of things. Expand career opportunities. To stay a student. To get "Dr." in front of your name. Be open minded about what you're researching and focussed on the task at hand. Treat it like a job: when you're in the office/lab/library, don't procrastinate and waste time. Do stuff. Take time off; go on vacation. Watch your mental and physical health. Both of these things can suffer in grad school -- if they are, take a step back, take some days off, make time to do fun stuff. Don't work yourself to the bone -- life is short and you should be doing fun stuff and enjoying some of the freedoms that grad school gives you. Assuming STEM, as this is my background: supervisor is the most important person. Try to find someone who you get on with; a strained relationship with supervisor definitely makes life more difficult (I had some experience here). Find out about money for traveling to conferences etc. Work environment (will you be in cubicle farm? small shared office?) and atmosphere (is everyone in 14hrs a day, 7 days a week? are people happy? do people look permanently tired/ill?). Talk to grad students 1-to-1 away from faculty to get some honest perspective on pros/cons of the place -- most will be happy to give you the low-down. If profs don't give you time/space to talk to grad students whilst at interview, take this as a bad sign. Again, from a STEM perspective, you'll be earning money. Probably not great money, but enough to live off. Many places (if you're a full-time grad student) won't allow you/be at all happy with you having another job. I know in my contract that I signed, it explicitly stated I couldn't have a second job. Often you can make some extra money teaching/TAing for classes, although the hourly pay is rough in reality.1. Why did you go to grad school?
2. When did you go to grad school?
3. What is a good reason to go to grad school?
4. What is a bad reason to go to grad school?
5. What is the best state of mind to start grad school?
6. What obvious and not so obvious things should I look for when choosing a program?
7. How on earth am I supposed to generate income while simultaneously committing enough hours to my studies? During the school year in undergrad I worked usually less than 10 hours a week.
I agree that in general, expanding career opportunities is a big part of education at all levels. However, I don't think that this is a particularly good sole reason for pursuing a Ph.D. -- my general impression from colleagues is that having a Ph.D. can be a hinderance on the (outside of academia) job market. I'd think in general (and of course, your mileage may vary...) that if improving career prospects is your main aim of graduate school, you're better off leaving with a M.S. and getting relevant job experience, instead of spending the additional 3-5 years on a Ph.D. (which is what I usually think of as "graduate school"). Another point to bear in mind, I think, is that if you're interested in academic jobs, it's also really worth being realistic at all stages of your chances. Very few Ph.D. students make it through to full-time academic positions and there is really no shortage of extremely well qualified candidates. I'm not advocating against this path, just it's worth having some back-up plan and gathering "transferable skills" for outside careers whilst in the academic pipeline.
I haven't tried any other job outside of academia since I started in the field, so it's a bit speculative, but I think that were I to enter the business field, I'd be better suited have gone through graduate training. I think a lot of people who already don't have good social skills go into lab work, and those already lacking social skills certainly don't improve them by spending five years with their head in a book or a microscope. But for the well adjusted, I actually think going through the process of self-doubt and discipline necessitated by finishing a dissertation can be character building, independent of the actual skills learned (which certainly won't be directly transferable to most fields).
I was traveling for work for a couple of weeks, so I've only just seen your reply now. I agree completely with your comments -- graduate training can increase how good you are at other jobs and be character building. I don't think it's a particularly good sole/major reason to go to grad school -- one would probably be better served by working in a particular industry instead, where one can character build and obtain relevant skills.