Although I didn't audition for any acting parts, I did audition and become a dancer at MK for four years...but this was from 92 - 95.
I don't think it matters what you wear, just make sure you look clean cut. No revealing outfits, no crazy makeup, big earrings, facial hair (don't know if you are male or female), tattoos (cover them up), etc.
For the dance auditions, they had us all learn a routine which we did in groups of about 8. After everyone finished that, they narrowed the group down to about 75 people (from about 500). Next they had us learn another routine while traveling down the floor and they then narrowed the group down to about 40.
The third step was the acting/lip-synching part. They lined up in groups of four or so, and had us act out a scenario that they gave us. It was pretty basic stuff. When that was over, they lined us all up and took a VERY long time to decide. They then separated us into which parts and roles they wanted us to be and that was it!
As far as a resume goes, if you have any experience at all (like classes, workshops, etc.) just put that on there. If the process is still the same, they had everyone fill out an application and attach their resume to it, so really more info goes into the application than the resume anyway.
Good luck!
