Asking a professor about his advisor When searching for graduate schools, I've found Professor A of University X with whom I'm interested in working. I'm also interested in working with Professor A's advisor, Professor B, who is at University Y.

Is it considered socially acceptable or a conflict of interest if I ask Professor A about how it was like to be advised by Professor B?
I don't see how it would be socially unacceptable. You might have to weigh the response you get from Professor A if you think he or she is keen to have you as his/her student -- but that often happens. The conflict often arises: the desire to do the best by the student in terms of suggesting other supervisors or institutions against the desire to have a good student working on a shared topic.

Regardless of whether you get Professor A's advice, seek out students -- current and past -- of Professor B and ask them for their opinions.