All PrC classes must have DM approval prior to being taken. Most will involve a quest of some sort before you may take a level in it. Also, at some point in the future, all PrC's will require a special token allowing you to take them.
It is in the players best interests to let the staff know as EARLY AS POSSIBLE that they may wish to take a PrC so that they can be observed for the desired RP. PrC's are special and are treated as such. Not everyone will get to play one.
To apply for a PrC, send an email to the DM email account and then inform us via the player communication section that you have done so.