Ask current students: What do you do for self-care? How are you supported by faculty in achieving self-care during grad school? What are your hobbies? (No hobbies or struggle to think of hobbies outside of work = red flag for me because of my own emphasis on work-life balance.) What is a way Dr. __ has supported you when things got tough? What is your current research/thesis/dissertation/project (and how much does it differ from advisor)? How free are you to explore research ideas that are different from Dr. __'s? Are most students funded through the program? Do most of the faculty provide paid research opportunities (or is it just assumed you'll work in the lab for free)? Why did you choose this program versus other programs?
Ask POIs: How do you view yourself as a mentor? How do you prefer to communicate with your advisees/lab (email, weekly meetings - this is to see IF this person even communicates with their lab regularly)? How many advisees do you have (if there are a lot, that may mean less quality mentorship)? Do you have regular individual meetings with advisees, or are these setup on an "as needed" basis? (Advisors who take the time to have regular meetings with their advisees are investing more time, which can mean better mentorship.) What are your advisees' career and research interests and how have you supported them in achieving/exploring those? --> I SOOOO wish I had asked this! It is easy for a potential advisor to say, "I view my role as supporting my students in whatever they want to achieve" but in reality have NO idea what their students' goals are and could care less because they are just focused on getting their minions to pump out more work for them. An advisor who can actually articulate what they know their students want to do, especially if it's not just a copy of their own research, means this is an advisor that at the very least listens to his/her students. I could have gone through my entire program without a single faculty member asking me what my research interests were and in fact, it was preferred that I didn't have any that would distract from The Current Lab Project. Also, what do most of your advisees go on to do? (Practice, research, academia? Can they name specific people and job titles? Do they even KNOW where their alumni are?)
In general: Don't be shy about asking about funding streams, how funding is allocated, etc. if you are aiming for a Ph.D., ask how common multi-year fellowships are and what are the typical sources of these (central campus, grants, departmental, donors). Ask whether research assistantships or teaching assistantships are more common sources of employment. Ask how assistantship employment is determined - is this an open application process, or are certain opportunities open based on your advisor? (My program's assignment of assistantships is opaque and often appears arbitrary.) Ask your POI if any of their current projects are supported by grants. Ask how often advisees are supported in writing grants. If your POI doesn't seem to know much about grants or seem to care much about grant writing, then they likely don't care much about funding their students, unless their students are somehow funded elsewhere.