Get all starters
To get all the starters (Bulbasaur,Charmander, and Squirtle), you will need two Game Boy Advances and another Pokemon GBA game. Start with Bulbasaur, then trade it to your other Pokemon game. After that, start a new game. Start with Charmander and trade it. Then, start another new game and start with Squirtle. Keep Squirtle and catch two Pokemon that you do not want. Trade them for the other two starters you traded to your other Pokemon game. You will now have all three starters.
Choose Bulbasaur Trade it to a friend. Start a new game, then choose Squirtle. Trade it to the same friend. Start a new game and choose Charmander. Trade it to the same friend. Catch four Rattata and one Pidgey. Trade three Rattata for Bulbasaur, Squirtle, and Charmander with the same friend. You now have five Pokemon (Bulbasaur, Squirtle, Charmander, Rattata, and Pidgey).
Starting Pokemon recommendations
Squirtle is Water type, and has an advantage over Charmander the Fire type starter, who has an advantage over Bulbasaur the Grass type starter. Note: Your rival will always choose the Pokemon with a elemental advantage over yours.
When you start the game and get to the point where you can choose any of the three Pokemon, your rival will choose the Pokemon that has the advantage over yours.
If you choose Bulbasaur, your rival chooses Charmander.
If you Choose Charmander, your rival chooses Squirtle.
If you Choose Squirtle, your rival chooses Bulbasaur.
However, if you have two Game Boy Advances, choose one, then battle your rival. Then start on the other game and choose the Pokemon that is your rival Pokemon's weakness:
If your rival has Bulbasaur, then choose Charmander
If your rival has Charmander, then choose Squirtle
If your rival has Squirtle, then choose Bulbasaur
However, it is a very good idea to have one Leaf Green version and one Fire Red version to catch all the Pokemon in the game, as you cannot capture the other six other Pokemon using just one game, depending on your starter.
If you started with Bulbasaur, you cannot catch Charmander, Charmeleon, Charizard, Squirtle, Wartortle, or Blastoise.
If you started with Charmander, you cannot catch Bulbasaur, Ivysaur, Vensaur, Squirtle, Wartortle, or Blastoise.
If you started with Squirtle, you cannot catch Bulbasaur, Ivysaur, Vensaur, Charmander, Charmelon, or Charizard.
Aerodactyl
To get the ancient Pokemon Aerodactyl, go to the house to the right of the Museum in Pewter City. Note: You must have Cut. Talk to the scientist and he will give you the Old Amber. Take it to the Lab on Cinnabar Island and let the scientist bring it back to life. It will be at level 5.
Articuno
Articuno can be found inside Sea Foam Islands. You will need HM Surf and HM Strength.
Deoxys
It is possible to get Deoxys at an island in which you solve a simple puzzle.
To get Deoxys, go to Island 9 and push the triangle forward. Deoxys will appear.
To obtain Deoxys, you must travel to Island 9. To do this, you need to obtain the Aurora Ticket, which can only obtained through a Nintendo Event, such as Pokemon Rocks America 2004. Bring your Pokemon Fire Red or Leaf Green cartridge to any of the events in Atlanta, Minneapolis, or Seattle to receive the Aurora Ticket. The same goes for obtaining Lugia, Ho-Oh (both on Island 8, requiring Mystery Pass); and Celebi and Mew (details unknown). Note: Ho-Oh can also be obtained via a link to Pokemon Coliseum.
Note: In the Pokemon Leaf Green, you will get the defense version of Deoxys.
Gyrados
Gyarados will learn Hyper Beam at level 55.
Mewtwo
Mewtwo is in the Cerulean Cave . There are also level 39 to 68 Pokemon there, such as Wobbofet and Magneton.
Moltres
Moltres can only be found at the top of Mt. Ember at Island 1. You will need to defeat Blamie first.
Zapdos
To catch a Zapdos, go to the Pokemon Center beside the Rock Cave. From the Pokemon Center, go up until you reach water. Surf to the Power Plant and go inside. Find your way around, and at the end you will find Zapdos, the Thunder type Legendary Bird.
Zapdos can be found at the Power Plant bellow the Rock Tunnel.
Legendary Dogs
The legendary dog that you get in the game depends on your starter.
Charmander: Suicune (Water)
Squirtle: Raikou (Thunder)
Bulbasaur: Entei (Fire)
To get all three Legendary Dogs, get together with two friends before any of you start the game. Have one player get Charmander, another get Squirtle, and the other get Bulbasaur. Each of you will get one of the legendary dogs: Charmander, Suicune; Squirtle, Raikou; and Bulbasaur, Entei. Once each of you has their own dog, trade one dog for another. For example, player one's Suicune for player two's Entei; player three's Raikou for player one's Entei; and Player three's Raikou for player two's Suicune.
Johto Pokemon
To get your first Pokemon from the Johto Region, defeat the Elite Four. Go to Island 3, then go in the tunnel. Talk to the man and he will give you a Nugget. Go out the door, and there will be a small patch of grass. Walk around in it, and you will find your first Johto Pokemon.
Duplicate Pokemon
Use the following trick to easily reproduce rare Pokemon, such as Charizard, Lapras, etc. Capture a Ditto in Pokemon Fire Red or Leaf Green. These can be found in the cave at Cerulean. Transfer your Ditto to Pokemon Sapphire or Ruby, then take it to the Daycare couple in Mauville and leave it there. The quickest way to get an egg is to cycle back and forth a few times in front of the Daycare Center until the old man comes out of the gate. The egg he gives you will hatch into the first evolution of whatever Pokemon you put into the daycare. For example, a Charizard will give you a Charmander. Trade with friends to get the other starters, breed an egg, then trade back. The hatched Pokemon will have you as the original trainer.Some Pokemon will not breed in this way, even though they have a gender (such as Latios and Latias).
Exp. Share
At Route 15 inside the big place, go upstairs talk to Professor Aid. If you have collected at least fifty Pokemon, he will give you the Exp. Share. The pokemon holding this item will gain the exact same number of experience points. For example, if Magikarp is holding it it and your Charizard just went up to level 59 and the experience was 496, then Magikarp will gain exactly 496 points.
Master Ball
The Master Ball can only be located by saving the president that is in Saffron City, by defeating the leader of Team Rocket. After defeating him, talk to the president. He will give you the Master Ball. It will catch any Pokemon without fail.
Nuggets
Go to the last person (Team Rocket member) on Nugget Bridge. Lose to that person after you get the Nugget. Repeat this until you have the desired number of Nuggets. Note: If you save the your game after defeating him, you will no longer be able to do this.
Repel and Super Repel
Repel and Super Repel will keep all wild Pokemon of a lower level than the first Pokemon in your party from attacking. However, if the wild Pokemon is of the same level or higher, it will attack. Due to the decreased amount of Pokemon to fight, you will have less random encounters. To exploit the use of this, go to a cave with high level Pokemon such as at Victory Road or Union Cave. Use the Repel once inside. Find a boxed-in type of corner and tap the D-Pad gently towards a wall. If done correctly, you will not hear a bumping sound. Doing this should not reduce the number of steps remaining on you Repel counter, because the Repel only counts movement that causes the character to take a step not turning. Just turn into a wall to make it easier for beginners. This trick is useful because you are always facing a Pokemon that is of equal or greater level, allowing you to get levels much faster than usual.
Running Shoes
Follow through Viridian Forest, go to Brock (the first gym leader), and defeat him. Brock has three Pokemon: Geodude level12, Onix level 14, and Geodude level 11. Then, go to the path that leads to Mount Moon's base. Try to go past the man standing slightly past the entrance. He should stop you. He is Professor Oak's assistant. After talking to him, he will give you the Running Shoes.
Your aide will give you the Running Shoes after the first gym.
Sacred Ash
Go to the Naval Rock Island (if you have the Mystic Ticket), and to the location where Ho-oh confronted you. Use the Itemfinder and it will automatically dig up the Sacred Ash, just like the Macho Brace at Viridian Gym after Giovanni left; and the Top from Pokemon Tower after Mr. Fugi left.
Silph Scope
Go to the underground path in Lavender Town and it will lead you to Celadon City. Then, go to the Rocket Game Corner. There will be a grunt looking at a poster. Defeat him, then select the poster.
Defeating Blamie
In order to battle Blamie the Fire Pokemon trainer (seventh gym leader at Cinnabar Island), you will need the secret key that is found inside the Pokemon Mansion that will open the door. You should have any Pokemon that are strong enough to withstand Fire attacks such as Flamethrower, Overheat, Firespin, Fire Blast, Flame Wheel, and Ember. Get Water pokemon and teach them Surf any and attaks that will cause poison, confusion, and other statuses to win the battle.
Defeating Giovanni
An easy way to defeat Giovanni in all battles is to use a Water Pokemon with Surf on all his Pokemon.
Get to One Island
To Get to One Island, defeat the Cinnabar Island Gym Leader, Blaine. When you come out, Bill will take you to One Island and give you the Tri-Pass. This will allow you to return at any time by taking the Pass to the boat dock in Vermilion City.
Getting to Saffron City
Go to the Celedon Department Store. Buy all three drinks on the sixth floor. The guard will not let you win. In order to get in go to the Mansion that is next a man talking about hot tea, go to the Right side of the Mansion. Enter, then talk to the old lady. She will give you the Tea, and you can now enter Saffron City.
This trick requires two Game Boy Advances, a link cable, a Pokemon Ruby or Sapphire game with a "Fresh Water" in the pack, and a Pokemon Fire Red or Leaf Green game that is completed and able to trade with Pokemon Ruby or Sapphire. Also, you will need another Pokemon Fire Red or Leaf Green cartridge. Give a Pokemon a Fresh Water. Trade the Pokemon from Pokemon Ruby or Sapphire to the completed Pokemon Fire Red or Leaf Green game. Take the Fresh Water and attach it to a Pokemon not from Pokemon Ruby or Sapphire. Trade it to the other Pokemon Fire Red or Leaf Green game. Give the Fresh Water to the guard. You can now access Saffron City easier. You can also do the same thing without the Pokemon Ruby or Sapphire cartrigde. Also, it works better when you have the completed cartridge and your friend has the unfinished game.
Safari Zone
When you get in the Safari Zone you will need to pay 500 to enter and will receive 30 Safari Balls. You cannot use any Pokemon. All you can use is Ball, Bait, Rock, or Run. Ball is to catch the Pokemon, Bait is to give the Pokemon food, and Rock is to throw a rock make a Pokemon angry. However, they will not use an attack on you.
Unlimited Safari Zone time
Enter the Safari Zone, then walk into an area and stop in the grass Then, tap the D-Pad, but do not move You will find the Pokemon in that area without wasting steps.
Find one location in the Safari Zone that suits you. Then, just rotate in place. Random Pokemon should you attack you every few rotations.
Easy money
To get easy money, use a Meowth with the Pay Day attack in wild or trainer battles.
Finding Selphy
In the Lost Cave, start from the beginning and go right, up, down, down, right, left, down, and right. When she sees you, she will fight with two level 49 Persians. Afterwards you will go to her house and ask to see a Pokemon (Arkanine).
Determining Pokemon's feelings towards you
When you use an item on one of your Pokemon outside of a battle, such as a Potion, the Pokemon will either move closer or away from you in the short intermission sequence. How far the Pokemon moves depends on how much it likes you. If it does not move at all, it feels neutral.
Trainer name comment
At the Pokemon Trainer Fan Club in Saffron City, the blonde man in the back will mention the last person you battled in real life. For example, if you battle a friend who named their character "Dusty", he will say, "Dusty's cool, huh? I love the way he talks. I'd really relish a chance to meet him in person once."
More than one attempt when catching a Legendary Pokemon
When you are close to a Legendary Pokemon and want to catch it, save the game just before you battle it. If you accidentally make it faint, Just reset the game and try again.