Pokémon Red Version, Blue Version, and Yellow Version - Walkthrough - Viridian City
This information might be useful when playing Pokémon FireRed Version and Pokémon LeafGreen Version, too.
Since you spent most of your time training your Pokémon, its time to heal it in the Pokémon Center (the building with the "POK" sign). Also, go to the Pokémon Mart and buy a few Poké Balls, since you can now buy items there. (Poké Balls are what you use to catch Pokémon. You can go down to Route 1 and use them.) You may choose to go west to Route 22 for a while.
Once you’re in Viridian City, talk to the old man to the north side, and answer No to his question to learn how to catch a Pokémon. Go north to Route 2.
Once in Route 2, go through the gate, and you’ll reach Viridian Forest.
Viridian Forest is a natural maze of trees and grass. The trainers use bug-type Pokémon, and you’ll find some bugs of your own to catch. The Pokémon are normally weak. However, you may have trouble defeating them using Squirtle. In Pokémon Red Version and Pokémon Blue Version, try catching a Pikachu.
Note on trainer battles
In a trainer battle, you must defeat all of the Pokémon that a trainer has. You can’t run away from a trainer battle, and you can’t use your Poké Balls to take the trainer’s Pokémon. When you win, you get an amount of money (which is why it is a good idea to battle trainers).
When you’re out of the forest, go through the house, and north to Pewter City.