I can usually play an entire day of vocal auditions and encounter only one or two singers who don’t provide music in a binder. Loose pages can fall off the piano, and books rarely lie flat, so binders are ideal.
Pro tip: If you frequently use an anthology book, I highly recommend taking it to a copy shop and having them replace the glue binding with a spiral binding. My shop does it for under $3.
Laying out pages to minimize page turns is by no means necessary, but if you’re striving for a perfect audition, it’s one detail you can take care of with minimal effort. You know what they say: “Happy accompanist, happy life!” (OK, I made that up.)
Two pages
Lay out pages side-by-side, not back-to-back. You laugh, but it’s happened.
Three pages
Tape pages 2 and 3 together with scotch tape.
Four pages
There are two possibilities for four-page pieces. The first option eliminates page turns entirely, but occasionally this layout doesn’t work if: a) the music stand isn’t wide enough, typically on an upright piano, or b) the piece requires playing at the extreme ends of the keyboard.
The second option is acceptable as well. Pages 2 and 3 should be double-sided or taped together. 
Five+ pages
Anything more than four pages should be double-sided.
When I began working as an accompanist, I was surprised by how informal my employment arrangements were. Some employers required tax forms and/or time sheets, some asked for invoices, and others needed no paperwork at all. The hourly rate varied widely, ranging from babysitter wages to professional musicians’ wages.
Eileen Huang 