Getting a Master Ball:
What you need to do to get the Master Ball is go to the first floor of the Pokemon lab and see Professor Krane. When you talk to him he'll open a secret passage hidden in the floor which will lead to a room which has a chest in it. Inside the chest you'll find a Master Ball. If you haven't been to Citadark Isle at least once you won't find anything in the chest. The Master Ball is best saved and used when you encounter Lugia.
Getting a Premier Ball:
This ball is simpler to get, just go to a shop and buy 10 or more Pokeballs and the shopkeeper will say 'Thank you! As a bonus have a Premier Ball!'.
Added by: Sanzano Sep 28th 2007, ID#7939