Beat Your Rival
To always beat your rival, you must have 2 games and 2 gameboys. First, you choose any starter in one game(Charmander), then the one your rival picks will be its weakness(Squirtle). On your otyher game, pick the final one(Bulbasaur). This is where the other gameboy comes in. You must go catch another pokemon, then trade it with your other game. You will then have two pokemon(Charmander and Bulbasaur). Train them and when you meet your rival, use the one you got in the trade(Bulbasaur, Ivysaur, or Venusaur).
Celebi, Jirachi, and Mew
You cannot legimitately catch Jirachi on Fire Red at all. You can only obtain it through the game Gale Of Darkness on Gamecube when you use the bonus CD to download it to your file on GD. You can then get it registered on your fire red's pokedex through battle and then trade it. (You cannot trade it to fire red if the entry doesn't exist)
Celibie
How do you get celibie 1st u must need 8 badges and now wat u do is after u get beaten by the pokemon league go back and talk to professor oak he will battle u and if u win he will give u celibe lv 50 /it is a grass pokemon very good moves wat it no's is solarbeam.mega drain.mega punch. mega kick
Cerulean Cave
Look for pokemon such as Golduck Lv49-63,Psyduck Lv30-49,Electrode Lv49-63,Magneton Lv49-61,Wobbuffet Lv55-68,Kadabra Lv49-59,Ditto Lv50-63,Primate Lv49-61,Mewtwo Lv70,Mew Lv50 P.S.Defeat Elite four 12 times and search for Mew in cave.Trust me.I already have all the pokemon from this cave.
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.
Black Belt
After you get to One Island, travel up the path called Kindle Road and go towards the volcano. Along this route, you will encounter several trainers with Fighting-type Pokemon. Have your Pokemon use Thief to steal a Black Belt from each of the Pokemon. After you have a Black Belt, take it off your Pokemon and use the VS Seeker to fight the opponent again. Steal another Black Belt from his other Pokemon. Every Fighting-type on this route is equipped with a Black Belt, which boosts the power of all Fighting-type moves.
Poison Sting
The Poison Sting attack can always poison if you press and release A at the exact time.. Time it by looking at one of the bubbles. For example, fight a Mankey. The one that crosses the hand to the left of the screen is the one to time it by, by pressing A just as it starts to pass the hand and releasing it just as it pops. It always poisons the enemy. This works for all Pokemon with the Poison Sting ability against all enemies, except for Bug types. Also, the Constrict attack can always get criticals if you press and release A twice while the vines are pulsating.
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. Additionally, 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.