A couple years back I wrote the instructions on how to become a GBAtemp moderator.
(See attached link)
You see how well it worked for me.
But in all seriousness the steps to becoming part of the staff are as follows.
!: Do not ask to be a part of the staff.
3: Report problems.
4: Be courteous.
5: Don't engage in trolling or flame wars.
6: Do not ask to be a part of the staff.