Should I sit, lie down, or stay standing the whole time?
You might think I'm kidding on this one, but I'm not. I've had people lie down in auditions - let's just say, I don't recommend it. I suppose using a chair and using a combination of standing and sitting is appropriate, and does not become distracting, but if you get to the point of lying down, I think the person hearing you may become distracted to the point of not actually listening to you! Any aria that is sometimes done lying down in performance (i.e. Vissid'Arte) can be done very successfully standing up in an audition.