An audition is not like a job interview, it is a job interview. As an actor, you should treat it as such. Dressing appropriately, being polite, and coming prepared are all important aspects, but perhaps the one facet that is most often overlooked is the necessity of being on time.
When your agent gives you a scheduled time slot, that is not the time that you should be walking in the door. That is the time you should be ready to go in the room. If an actor is scheduled at 10:15 and is walking in the door at that time, it can set everybody back. There are info sheets to fill out, potential script changes, and, at times, the need to be paired with another actor so rehearsing is beneficial to you both.
There is an allotted amount of time given to each audition. If you are late or have made the session director wait for you, that cuts into your time and an extra 30 seconds could be the difference between getting an extra take. If you walk into the room with a purse, a laptop, etc. and spend time trying to get yourself organized, this cuts into your time. It is part of being ready. If you do enter the room with personal items, please do NOT place them on the set (which is basically any area in front of the TV monitor). If you are planning on taking your jacket and glasses off for your performance, do it before you enter the room.
We can only see the best in you when you are prepared. And we always want you to do your best.