What is your age, and what type of production is it for? (high school, college, community theater...?)
Well, anyone who can sing and has brown hair, I would say go for Belle!
But really, although it sounds trite, any part is a good part in the show, the chorus does a lot, and enchanted objects are always fun.
Do you have to state what you are auditioning for? If not, just go wow them as best you can and let them decide.
Songs- there are quite a few posts about that already, and I can't remember what people have done or suggested, so maybe browse some other audition posts here. I sang a shortened version of "Just around the riverbend". I thought it went well and is a great audition song, but the director went another direction for Belle.