As an actor you will know just how difficult it can sometimes be to get a casting call or an audition. It is very competetive out there and acting jobs don't come along every day (unless you are very lucky). When an audition finally comes along you owe it yourself to be as prepared as you possibly can be.
Be punctual for your audition. Make sure you find out exactly where you are going and how to get there. Leave yourself plenty of time in case things don't go according to plan. Remember it's far better to be sat in the waiting room going over your script one last time than sat on the number 11 bus in a blind panic because you are not going to make it.
Know your audition speech. It sound obvious but don't expect you can just wing it and paraphrase. There is every possibility that someone on the panel will know the play you are reading from and will wonder why you are deviating so much from the text.
Wear something sensible to your audition. There are various schools of thought on what to where when it comes to auditions. Some directors prefer you to dress in character, for others this is not necessary. Whatever you decide, make sure you are wearing something appropriate. Pink high heel stilettos are not an ideal choice for Lady Macbeth, (unless of course you intention is to contemporize your speech)
Know the play. If at all possible read the play before the audition. The director may well ask you your thoughts on the character etc. This is a difficult question to answer if you have no idea what the play is about. If the play is new writing see if you can find any earlier work by the play wright and try and use this as a talking point.
Never apologise. Many directors and casting directors hate it when you say something like "I'm sorry but I have a really bad cough just now". This sounds like an excuse for the quality of you performance. If you do have a bad cough or cold, the likelihood is they will realise and possibly take it into account, but don't draw attention to it yourself.