An audition is in every way, a business interview. Your interview begins the moment you walk in the door. In fact, the first 10 seconds tend to be the most important. Aside from the obvious talent screening, auditioners want to see what kind of a person you are and what you might be like to work with. An auditionee who is comfortable with themselves and sincere in presenting themselves will have the upper edge before they even begin to sing.
Appearance is critical when making a first impression.
In fact, many musical theatre auditions will do a visual scan before they hear auditions and only invite certain 'types' to sing or read. While it is important to stay true to who you are, you need to be honest with yourself and know what to enhance. Make sure your pants are not too long or short. Wear socks that match and don't distract from your outfit. They tend to look juvenile and very unprofessional.