Instructions
Beat the Elite Four at Victory Road to be declared the champion of the Johto region. Go to Olivine City and board the ship to Kanto.
Travel to each city in the Kanto region and defeat each Gym Leader to earn their badges. You cannot challenge Red without all of the badges.
Go to Pallet Town and enter Professor Oak's lab. With all the badges he now tells you to take on Ash, which opens the road to Mt. Silver.
Put all of the Pokemon in your team that you want to use in the battle. This is generally your highest level Pokemon, since Ash's Pokemon are very highly leveled. Use a Houndoom, if you have one, and at least Pokemon that knows Thunderbolt. A fighting-type Pokemon such as Machamp is useful, as well as the psychic-type Alakazam. A Pokemon that has learned Earthquake is helpful as well.
Go to Mt. Silver and enter the dungeon. Work your way through the dungeon until you reach the final room where Red awaits. Put the Pokemon that knows Earthquake first in your lineup before speaking to Red.
Use the Earthquake move immediately when Red sends out Pikachu. This is likely to knock it out in one hit. Next, Red sends out Venusaur. Switch to Houndoom and use its Flamethrower move to kill the Venusaur.
Use Houndoom's Crunch move to knock out Espeon. When Snorlax is sent out, use your fighting-type Pokemon. Snorlax can heal itself, so use your most powerful attacks to knock it out before it does so.
Knock out Ash's Charizard by using a Pokemon's Surf move and then defeat Blastoise with the Thunderbolt move. After all of Ash's Pokemon are defeated you have won the game.