I'm not a member but did have a look at their website a little while ago. I'm pretty sure there's a section on there somewhere with audition advice and that kind of stuff. Its not hugely informative I'm afraid, but its a start.
from what i remember, it said something like they are not expecting you to be the best magician in the world, but you must be able to perform sleights well and must have a good patter and performance style. Again, this is just from memory, so don't quote me on that. I'm sure there's people on here who will be able to help you properly

best of luck (not that i think you need luck of course!)
Will