Tips for performing in front of judges?

When I have to do an audition in front of judges or even an audience where the faces of people are easy to see, it always really gets me nervous.
I remember I auditioned once in front of judges and ended up sounded really bad because the nerves strained my voice. Soon I will audition in front of judges again, but I really don't want the same thing happening this time.

Does anyone has any tips on this? I think it would help to avoid eye contact with the judges, but I'm not sure if that's rude. >_<