With the exception of capstone advice (see below), I've written almost no general advice. But I have benefited enormously from others who have. The following list includes works that have inspired me as a scientist, educator, and person. Maybe they will do the same for you.
Richard Hamming's talk "You and Your Research".
"My Rules of Thumb", Greg Mankiw's description of how he works.
The "Advice for Students" section of Greg Mankiw's blog, especially "How to Write Well", "Should grad students teach?", and "Good Academic, Bad Human Being".
Steven Weinberg's "Four Golden Lessons" for scientists, especially those in graduate school.
Nancy Kanwisher's site, particularly her section on Mentorship.
Randy Pausch's Last Lecture: "Really Achieving Your Childhood Dreams".
"When Truth or Reason Are No Longer Enough", Alison Gopnik's meditation on the tension between pursuing liberal Enlightenment values and staying connected to family, community, and culture.
Linda Holmes' "The Sad, Beautiful Fact That We're All Going to Miss Almost Everything".
Alec Baldwin's interview of Guillermo del Toro. The director talks about trusting a creative team, creating art through constraints ("a hostage negotiation with reality"), investing in one's work, and interleaving projects of different types and scales.
Bill Hammack's adaptation of Michael Faraday's "The Chemical History of a Candle" lecture series and his own "The Things We Make" about the engineering method.
Below you’ll find some general advice about capstones, which is most applicable in the early stages of project development but which remains relevant throughout the process. I initially e-mailed these thoughts to some capstone students on 29 April 2016.
Read about potential areas of interest, and get to know your potential capstone advisors better as researchers by acquainting yourself with their work. I often go along with the adage that reading rots the mind, but a little exploration can go a long way at this point. See whether a given topic still interests you once you’ve gone down the rabbit hole a bit.
Talk or correspond with potential capstone advisors. (When? By reading week of Year 3, Sem 2 would be good.) Such discussions will allow both parties to get a better sense of the intellectual and stylistic fit. You likely have an idea of these aspects already, but the considerations here are a bit different from choosing a course instructor or just having a conversation. You are looking to generate mutual interest and mutual commitment.
Think very hard about what you want to get out of your capstone experience, and be strategic to further those goals. Of particular relevance is deciding to what degree you want to align yourself with your capstone advisor’s expertise and research aims. I’ve run the gamut from both the student side and the advisor side, and there are trade-offs to keep in mind. If your primary aim is to develop and address your own question, then realize that you will have to be more independent in navigating the literature, designing and implementing the experiment(s), and staying motivated through a long slog. If your primary aim is to develop a publishable piece and/or get a better idea of how a psychologist works and thinks, then you may need to co-develop or select a semi-developed project instead, with the advantage being that you can then better leverage your advisor’s topic expertise, existing experimental threads, and excitement. My hard-won advice is to lean towards the latter, and some capstone advisors will insist that you do.
Keep the scope reigned in. PhD students frequently have to be reminded that their dissertation need not win a Nobel Prize or shake the very foundations of their field. A PhD dissertation is a major personal work of scholarship, representing a solid and coherent body of work that makes an intellectual contribution to a given field. Such a substantial yet measured aim is the goal of multi-year, full-time programs, so keep in mind that your capstone should be something much more modest and circumscribed. This doesn’t mean that you shouldn’t address big questions, just that you should be realistic about what time, interest, and experience allow in terms of implementation. Some advisors—myself included—build a list of potential projects that can give you a better idea of what we think is doable. These potential projects are the “semi-developed” ones to which I refer in point #3. Looking at capstone projects from previous years can also be helpful.