After the auditions the directors spend a long time reviewing the audition tapes so don't expect to hear anything immediately. Often if you don't hear anything then you can presume you haven't got a part. Wherever possible you will be contacted so you know where you stand.
Due to the numbers involved it is more likely that you wont get a part. This is because there are often many people going for the same role.
Don't be too disappointed. There will be many reasons that you weren't successful, even if you did the perfect audition. You also may be offered a smaller or extra part instead.
If you are fortunate enough to get a leading role you will be personally contacted to see if you are still keen. If you want to accept the part and your family are happy to support you, then an information pack including permission forms, medical forms and agreement forms will be sent along with a copy of the script.
If you are under 16 then your parents will need to be spoken to as they will play a big part in transporting you and encouraging you through the project.