I will simply pepper them with questions in email to get their reactions to the story as a whole
Ha! Yes, I think that's the way to go. :)

However, I'm aware that my natural tendencies are not always what an author wants and it's a lot easier to figure out what to give them if they ask for it up front.
I think that's key. Before I even look at someone's story, I ask them a series of questions: what are you concerned about, what do you think needs looking at the most, was anything problematic for you, etc.