Unfortunately, occasionally, something said in a casting room can get into your head and effect your performance. Try to develop some techniques so if it does happen, you aren’t thrown by an off comment.
Remember, the casting tape won’t show the CDs comments or the attitude of people in the room, only your scenes on tape, so how you handle yourself is most important.
If they don’t like the way you have done something, that’s fine! Think of this as an opportunity to try something new and show how well you take direction to change things up for them. Similarly, don’t be put off if you are asked to radically change things in your performance. This is often because they want to see your range and ability to take direction and not because they didn’t like your initial ideas of a scene.
It is also important to remember, CDs work VERY long days, often to very tight deadlines with very demanding clients. They really do want everyone they bring into the room to do well (as it makes them look good if their casting is great), but often they can be grumpy or very direct (especially on commercials if they have seen a new person every 5 minutes for 6 straight hours already). It really isn’t you, so you just keep professional, do your job and have a little understanding for them. Follow the 4 Ps and you won’t go wrong.
The biggest thing that can plant doubt for an actor is differing character descriptions or people in the waiting room who look nothing like you. The CD has chosen to see you over thousands of submissions and they have seen your headshot/reel. They may have had a discussion with the director about another possible way of imagining the character, you never know what they want.. Every opportunity in front of a CDs is a chance to advertise your skills and is never wasted.
Doubt is one of the biggest blocks to a good performance, so if you have any doubts about why you have been chosen, TRUST THE PROCESS. I am not sending you there to waste time, so have already made sure you are what they are looking for. If you have any doubts about how to perform a scene - ask the CD so you have clarity and can do a brilliant job!