From Excerpts of Notes from Lesly’s Monday Ongoing class on 8.22.11, courtesy of Jennifer L.:

A casting director friend says the most common mistakes actors make in auditions are:

• Doing nothing out of fear of being too big or making the wrong choice. He wants you to give him a choice even if it’s wrong because he can take that and change it. But he will not mine for a performance.
• Showing up late. [Note from LK: yes, this is ironic given that you usually have to wait forever to read, even if you come on time. But that’s the biz.]
• Coming in unprepared. He saw Amy Adams on and off for seven years and it just always ended up going another way . . . but when it was her time, she always came in prepared, on time, made choices, and made the material better than it was. So when it was her turn? It was a slam dunk.