You have pretty much got it figured out already!
All you can do is talk to as many people as possible, and study as much as you can, its luck of the draw.
I always found schools placed emphasis on having the same instructor all the way through. I found this to be rubbish and where i finished my ppl I had any number of instructors, some i found great in the circuit and others at nav etc. We were also encouraged to politely request a different instructor with ops should any conflicts of personality arise or you simply didnt feel that your particular tutor was as good at any given area of the sylabus.
You should never be afraid to speak up and request or even demand what you require from an fto. at the end of the day its your money and if you are considering a proffesional career you will be required to make such awkward decisions.
All the best with it
RED WINGS