First, you have to make a large cash donation to the site owners, or agree to co-sign one of their loans. Then, there's the credit check, criminal background check, fingerprinting, DNA test, and certification exam. Finally, there is a week-long period of cruel, sadistic hazing by the other moderators.
Actually, the link provided by Hara and An t-iasg pretty much explains it all.
There is also a new addition to the staff called Mentors. These folks are recognized for their knowledge and willingness to help other members, especially newbies.