How to succeed at a musical audition
In my experience on both sides of the fence as performer auditioner, I feel the most interesting aspect is that you just need to be yourself initially. Don't go into an audition with a 'big head', or trying to make out you are better than anyoje as it will come across, just be ordinary and don't make a fuss. Secondly,and this is the big one, always choose a songs that are in different styles, that is to say, normally: (i) Up tempo song (ii) A ballad. It proves your worth as a singer, shows how you can deliver the songs, and ultimately your technique, your stamina, breath control diction, characterisation. Also, cheoose different songs, songs that are rarely done for audition, instead of the same stream style songs. The audition panel get fed up after the fiftieth 'les Mis' song, a song from the fifties musical 'Salad days', for example, will be like a breath of fresh air, and that you took the initiative to be different will look well. Have spare copies of the songs ready, take two of each, and have a third song ready (now this could be a Les Mis piece for example!), in case you are asked to sing something from the show you are auditioning for, have that ready too, unless it's a requirement for the audition anyway
Performance and energy is the key. Going into an audition 'flat', lacking in energy or performance shows, big time. It may only last a few miniutes, or seem like it, but you have to go in looking positive and full of energy. A good characterisation and acting is extremely important. Research your character, and find out everything there is to know about that character for your song, as they may ask questions. A low voiced singer may prefer early morning auditions when the voice is at it's best. The higher voice (tenor foe example), may prefer a afternoon audition when the voice is settled and easily warmed up. If you are offered a room to warm up your voice, take it, use it, and if you can get hold of the pianist for the audition get a 'run though' before hand so he get's your style and tempo for example, always an idea to ask when you arrive. Take water with you, even into the audition room, as some, surprisingly, never have any water available.
Inside the audition room, if you make a mistake, or you are not pleased with how the song is going, ask if you can start again. However, knowing your songs well will go a long way at a successful audition.