Patsy, where did you hear that wearing your hair up for an acting and singing audition is "recommended"? I think you should wear your hair the way it is most flattering. Also, some musical theater schools ask for two monologues, so keep in mind that you want to be able to get into character for the second (when it is required) without having to leave the room to change outfits.

Re: heels. Again, wear what you are most comfortable wearing. As someone said above, the important thing is that *YOU* feel attractive and as if you are putting your best face forward. (I have heard that NYU asks kids to kick off their shoes and audition barefoot. But as far as I know, that's the only school that asks that.) One last thing: many MT programs also require a dance audition. So factor that clothing change in when you are figuring out what to wear. Best of luck!