In the dozen years I have spent attending auditions I have seen every variable from ripped jeans coupled with midriff-skimming tops to (I kid you not) full-on evening dress teamed with white trainers. I would advise aiming for smart clothes, whilst remaining as comfortable as u can be. Now is not the time for your favourite slogan t-shirt proclaiming you as a "badass" or a "princess in training".. You cannot go wrong with a pair of smart black trousers and a shirt/blouse if you are really unsure of what to wear. I'd advise not to go down the road of wearing "your lucky" outfit either. The zip broke on my "lucky" dress the morning of my LSO audition and I actually had to do my dress up at the back with about 20 safety pins and threw on a cardigan to cover them. Ridiculous, as I spent most of the time worrying about the integrity of the pins rather than on my performance. Have a couple of choices to hand so that you are not caught out and do play through your audition in your outfit and shoes to make sure you are completely comfortable. Bring a second layer incase it's a venue that is very cold.
Above all, try to relax and enjoy it! If that fails, apply for a job abroad and play behind the screen in your PJs..
You might be interested in attending Maxine's webinar on Looking Good - The best outfits for concerts and stage make up on February 4th at 8:30pm. More information and sign up here.