No, it wasn't my bare midriff or my too short skirt!
My faux pas were:
1.) Not smiling and saying hello when I entered the room - I was so nervous I had to strive to keep from bolting out the door, inanely blubbering "Eighth notes? Sixteenth notes! ...SYNCOPATION!!!!?...Gah!!!!"
2.) I certainly wasn't of good cheer when I chipped notes or made mistakes.
3.) I was so mortified by falling apart in the audition room in front of 20+ people that I don't recall saying "thank you" at all, although I did apologize to the audition coordinator for wasting their time, which was probably not the right thing to do or say, but under the circumstances, I felt it was warranted.
This is a very cool topic that you have brought up. Not only is it necessary to prepare musically and hopefully mentally, but there are certain other things that have nothing to do with music that can be equally as important.