What to ask when asking for feedback

What kinds of questions do you ask of your beta readers?

I'm currently in Month 2 of the 5-Year Plan, so I’m new to this whole “being vulnerable” and “sharing your work” thing. I have sent my first short story out to my Timothy… and he loved it! Since then, I have sent it to quite a few more people and even included it as my first post to this awesome community (which you can read here). I'm getting positive feedback overall—which is great!—but I don't know what to ask to prod further and see where the story could use some revision.

What questions have you guys asked that leads to some stellar constructive feedback from your readers?