The first building you'll reach is the Pokémon Center. This Pokémon hospital will heal your team to full health and normal status, and Trainers are free to use the PC in the corner. In addition to accessing your item storage, these PC's can also access your Pokémon storage. Since you can only carry six with you at once, any others are immediately transferred to storage upon capture. It is typically a good idea to heal up and save your progress whenever you enter a Pokémon Center.
Behind the Pokémon Center is the local Poké Mart. These stores offer a variety of Poké Balls, Potions, and other items. When you step inside, the cashier asks you to deliver a package to Professor Oak. The cashier will not sell anything until the delivery is made, so take it back to Pallet Town.
The Kanto region, as seen when viewing the Town Map
Upon delivering the parcel to Professor Oak, his grandson runs in. Oak gives you both a Pokédex, a high-tech Pokémon encyclopedia. This little machine will record all available data on the Pokémon you encounter, and will be complete when you catch a member of every species. Stop by your rival's house to receive a Town Map from his sister Daisy before leaving town.
You may now buy Poké Balls and other items at the Poké Mart, and the old man that had blocked your way northward has had his coffee now. When you pass him, tell him that you're not in a hurry, and he'll show you how to catch a Pokémon. Before heading north, detour to Route 22 in order to battle your rival and catch some new Pokémon.
Here you run into the rival, who will challenge you again
Route 22 is a short route that runs west of Viridian. The path is a dead-end right now, but you can hunt for new Pokémon here. Not far along the route, your rival appears and challenges you to a battle. While his Squirtle or Bulbasaur have both learned a move of their respective type, only Squirtle's Bubble move inflicts damage, posing a threat to your Charmander.
If you beat Blue, you can head back to Pallet Town to get 5 Poké Balls for free from Professor Oak in his lab, but only if you have no Poké Balls in your inventory and have added no caught data to the Pokédex. After the battle, heal your Pokémon and then stock up on Poké Balls. Head north to reach Route 2.
Route 2 links Viridian City to Pewter City in the north. Much of the area is occupied by Viridian Forest, a large maze of trees. The east side of the route is inaccessible at the moment. Head through the gate to enter the forest, a whole new area with new Pokémon to catch!