WARNING: I don't know how reliable these codes are.
When you throw an ultra ball hold UP and B to turn Ultraballs into Masterballs.
To get Missingno, go to Cinnibar Island and trade with someone in the Pokemon Lab. Go to the West of the Island and surf along the coast. Keep going until you fight. The screen will black out for a few seconds.
To get Eevee, go to the back of the Celadon Mansion and go to the top floor. The pokeball on the table is Eevee.
To make fishing easier, hold A down while you fish.
To catch Ditto easily, pick a weak Pokemon like Magikarp and switch to another Pokemon when Ditto changes to Magikarp.
While attacking, hold down B and it will do 1.5 damage, but don't hold down B while your opponent is attacking, it does 1.5 damage to you!
To get infinite items you first have to have the item you want to duplicate on the 6th item down from the top of the list. Then find Missingo and fight him until he dies. Your item on the 6th spot will now have a symbol next to it. You can use that about 20 times or so before the symbol disappears an you will have 99 of that item. Keep using that item until you have just 1 left. Then go make a bunch of that item over and over again.
