That is some great advice. I was looking at the PhD program of my current school and they have a Student-Advisor expectation worksheet with stuff like a lot of the things you mentioned like freedom and meetings. In some schools, you do a trial project with your advisor too so that is probably very helpful in choosing an advisor.Well, it's difficult to really assess this before you actually apply and spend some time in the program. Many schools don't require you to make a final decision on a supervisor until the end of your first term. This gives you time to get to know the faculty a little. But again, the more you learn, the better.
It's important to look beyond just the subject matter that they study.
Consider how you learn. What type of professors do you learn the most from? Which ones do you struggle to understand? What type of hours do you like to keep? Do you respond well in a regimented atmosphere (i.e. 9 - 5 days, regular weekly meetings, a clearly defined outline of expectations, etc.) or do you prefer more independence (i.e. the freedom to come and go from the lab/office as you please, sometimes working late into the night, the ability to walk into your supervisor's office unannounced, etc.). Are you okay with online meetings or do you respond better face-to-face?
How much freedom do you want in defining the direction of your project? Some supervisors very much fall into the "do what I tell you and don't waste your time on anything else" class, while others lean more toward the "so what have you been up to over the last month?" Some students are flexible to this kind freedom/regimented spectrum, but others really struggle if the supervisor doesn't jive with them.
Look at a supervisor's other commitments too. How many other students do they supervise? If a supervisor has a dozen students, how much one-on-one time are they going to be able to commit to you? Are they planning a sabbatical in the next few years? Retirement? What committees do they serve on? What's their teaching load?
You can also look at current and past graduate students of theirs, if that information is available. (Often this is the kind of thing you find out on a campus tour.) Where are they ending up? Are they going into work areas you see yourself doing?
Considering the amount of other students the advisor has and stuff is also something important that I will keep in mind. I can never benefit much from group meetings but I do find a lot of value in one on one meetings based on my experience so far, so I will make sure to have plenty of one-on-one time.
Looking up their past students also seems smart. Would it be advisable to contact their past students?
Very good advice. Thank you so much.