It says the answer on the first page.
I think you have to beat another gym leader or another trainer from the guild.
[Edited by LoC_Leftie, 12/8/2008 4:36:20 AM]
There are no requirements. Just have a team and FC. If your team checks out legally, you have the position.
you can put pokemon from FireRed, LeafGreen, Ruby, Saphire, and Emerald on to pokemon diamind and pokemon pearl