I am interested in this thread, as I too have been thinking about joining up at the local circle. I know an audition would be on the cards (no pun intended) and any advice given here will be helpful to anyone thinking of doing the same. Even for auditions for work maybe.
I have had a slight (honestly, no pun at all) interest in magic for years, but over the past 2 years I have built up a fair selection of effects including a growing number of non card illusions that are getting better responses all the time. My card magic goes from strength to strength and I am coming up with new ideas for reveals amongst other things.
The hardest part i imagine in showing magic for the first time to seasoned pro magii is overcoming, "but they'll have seen it before". I am lucky in that my uncle was a magician for many years, and likes to see any trick I've either come up with or learnt. Even if he has seen it, he gives good pointers on performance and patter too. Oh, and luckily it was in front of him that I learnt not to do cloth vanishes in front of light sources, even sun lit windows....he laughed his head off as he could see exactly what I was up to, but we both saw this as a good thing because I had got this lesson out of the way without the shame of it being at a public performance.
good luck with your audition king_of_keighley and have fun with it.
I know when mine comes around, I will as already suggested keep to what I know well but vary as much as possible(maybe I will get a chance to tryout newer material later in the evening, who knows) and if I get flustered, take a breath and carry on..... long enough to compose and just a little shorter than a pregnant pause should do it.
If all else fails, advice I heard for interviews once went along the lines of imagining them on the toilet to break your conscious divide between you and those you hope will ultimately allow you access.
Quite how this works with a room full of people I have yet to find out
