Pokémon Red and Blue/Viridian City

'Viridian City isn't exactly a bustling burg, but it's bigger than Pallet Town. There you'll see your first Pokémon Center, a place where you can go to restore your Pokémon to full health. You'll also see a Pokémon Mart, which stocks items useful to Pokémon trainers. This one has a delivery service and will need your help to make a special delivery.'

Arriving at Viridian City
Upon arriving at Viridian City, there are a couple of new buildings for you to explore. The very first building that you will come across is the Pokémon Center. It is in these centers that Nurse Joy will heal all of your Pokémon for free. You may also use their computers to access your item storage and change your Pokémon roster. Get in the habit of going here first whenever you enter a new town: you don't want to be unprepared for any of your rival's sudden challenges.

You can't go any further north beyond Viridian City for the moment; a sleeping man is blocking your way and won't move. Above and to the right of the Pokémon Center is the Viridian City Mart. During your very first visit, the manager inside won't sell you anything. He does, however, run a delivery service on the side, and will ask for your assistance in delivering a package to Professor Oak. It must be important, so help him out.

Returning Home So Soon?
Return to Pallet Town via Route #1 and enter the Pokémon research lab. When you deliver the package to the Prof., he will give you a Pokédex, a sort of digital encyclopedia with entries for every Pokémon — as soon as you fill them in.

Before you skip town again, head to your rival's house in the northeast. When inside, speak to his sister, who is far kinder to you than your rival ever was, and she will provide you with a Town Map, which shows your current location as well as the location of the other routes and cities. When used in conjunction with the Pokédex, you have one powerful Pokémon hunting tool.

The Rest of the Sights
Once you've completed your errand, return to Viridian City and go back to the Poké Mart a second time. The clerk will now sell you whatever you need now, and you'd be wise to stock up: since you lose half of your money when you run out of usable Pokémon (because they've all Fainted, for example), it doesn't pay to keep a lot of cash on hand.

Ah, and please don't buy Parlyz Heals nor Burn Heals now: they are useless at the moment, as there are no Pokémon able to burn you so far, and you can only be paralyzed by rare Pikachus (In Viridan Forest, Red/Blue). On the other hand, Antidotes may be useful, as Weedle can poison you.

You may wish to buy as many Poké Balls as you can afford (you'll be needing them), some Potions if you're running low (they're only for sale here in the Yellow version) and maybe an Antidote or two to play it safe, since there are plenty of enemies that can poison your Pokémon in the Viridian Forest.

The building immediately above the Pokémon Center is the Pokémon School. You can acquire some good tips by reading them off of the blackboard. There is also a Potion hidden behind the weird tree in the northwest corner of town.

If you head north, you'll find that the old man who was blocking your path has finally gotten himself together and out of your way. He will then proceed to give you a lesson on the proper use of Poké Balls. When he's finished, you can head past him to Viridian Forest, the area you'll have to cross to get to your next destination. Don't get him too far out of mind, however – you may want to visit him after getting to Cinnabar Island.

Using Poké Balls Effectively
You may want to go straight to Viridian Forest, but don't be too hasty! Route #1 was full of Pokémon that you can catch anywhere, but the area west of here, Route #22, has a few interesting finds, especially in Yellow. But don't go past the grassy area, or your rival might challenge you to a fight when you're not quite ready. You'll want to have a bunch of good Pokémon before you attempt to challenge the Viridian Forest. Spend the next few minutes tracking some down in Route #22.

Whether you're trying to catch all of the Pokémon you see or just the ones that you need, you should always be prepared for a chance encounter with a rare Pokémon. This means having at least 3 or 4 Poké Balls on you at all times, and at least one low-level Pokémon on your team.

The last part is important, since it's incredibly difficult to catch Pokémon when they're at full strength. They're a lot easier to catch when they're in the yellow damage zone, and a cinch when they're in the red, but you'll need a weak fighter to take them down to that level or you may accidentally knockout your target as you whittle away at its health. Sleep, Paralysis, and other negative conditions also make catching wild Pokémon easier.

Once you've caught them, Pokémon need lots of EXP to level up. Weak Pokémon who can't survive battles have a difficult time earning EXP. As a result, they can be hard to level up unless you use a little trick: simply put your weakest Pokémon at the top of your roster. When the battle starts, your weak Pokémon will appear to face the challenger. As your very first move, swap him out for one of your tougher Pokémon who can beat the challenger. The new Pokémon will do all the work, but since every Pokémon who appeared in the fight gets to share the EXP, the weakling will still get half! But beware: since you're using your first turn to switch Pokémon, your opponent will get the first attack.