Use RASP until Atma Weapon is out of MP to wound him. Another technique is to cast Vanish and Doom.
Defeating Wrexsoul
Take Gogo, a character that has the X-Zone spell, and a character with the Vanish spell. Make sure Gogo has the Magic skill equipped, and not Runic (it is useless in this battle). Cast Vanish on the two creatures, and then use X-Zone. They will die and you will win the battle. Your rewards are the Aura, Cyan, and the Alexander Esper. It is useful in battle against creatures such as Doomgaze, which is weak against Pearl.
Defeating Phantom Train
Use a Phoenix Down and the Phantom Train, a possibly hard Boss, is easily destroyed.
Defeating the Magi Tower Boss
After defeating the Atma Weapon the first time, cast Life 3 on everyone, have them all holding a Wall Ring as one of their relics (helps through the entire level), and have someone Berserk the Boss. After that he will only use regular attacks and will not change his weakness. Once defeated, he will use Ultima, the most powerful magic attack in the entire game, and it will most likely kill you.
Easy experience
Get an Exp. Egg and fight some Tyranos in the forests above the veldt at the World Of Ruin. Use Vanish, Doom or Vanish, X-Zone in the battle.
Quick MP
In the World Of Balance, go to the triangular island in the very top right corner. Keep walking around until encountering the invisible monster called Intangir. Simply chant death on it to gain 10 MP.
Getting good weapons immediately
When fighting with the Moogles at the start of the game to save Terra, go to "Equip" and remove the Moogles' good weapons. Equip them to yourself to get good weapons immediately.
Defeating Kefka for the final time
When fighting Kefka for the final time in Kafka's tower, throw the Atma weapon. He should either die or be weak enough to be defeated with one more hit.
Defeating almost every Boss
To kill almost every Boss in the game, cast Vanish then Doom to kill it. The Vanish makes the Boss always get hit by magic spells.
Give Gogo any commands
Go to Gogo's status screen. Look at his commands. You will see Mimic and three empty slots below it. Choose one of the empty slots and a list of all of the commands from the other characters you have will appear. Choose the one you want, then do the same with the other two slots. For example, you can have Mimic, Blitz, Tools, and Swordtech all at the same time, if desired.
More damage with Locke
Equip Locke with Offering and Genji Glove. Then, give him the Atma weapon Valiant Knife. Although this is best when around 4000 HP, he still does a lot of damage if less is available.
Getting the Paladin Shield
Equip the Cursed Shield and a Ribbon (so the effects of the Cursed Shield are negated). Fight 255 battles to transform the Cursed Shield into the Paladin Shield.
Getting the Chain Saw
In Zozo, when you find the clock on the top right side of the town, put in the following times. First hand 6:00, second hand 10, third hand 50.
Atma Weapon combo
This trick requires the Atma Weapon (Cave to Esper World), Offering (In World Of Ruin, Odin's Castle), and approximately 7,000 HP. The Atma Weapon powers up by your HP. With high HP you should be able to do 9,999 damage to every enemy (even Kefka). With the Offering, you will do this four times (39,996 damage) in just one turn.
Another Atma Weapon:
It is possible to get another Atma Weapon during the final set of battles. When battling the warrior with a woman's head above and behind him (just before god Kefka), steal from the woman's head. You should now be able to equip another Atma Weapon to a character.
Random hat replacement
Un-equip the hat of the character you like the most. Sell all other hats you have. Then, go to the hatless character's equipment screen and select "Optimum". Sometimes a random item (usually a Genji Glove) will be equipped as a hat, and boosts defense up to 255.
Stealing a Gengi Glove
On the floating continent in the World Of Balance, you can steal a Genji Glove from the Dragon. Bring Locke along and equip him with either a Genji Glove and the Thieve's Glove (or the Steal Ring and the Thieve's Glove). The dragon also carries a potion.
Getting the Soul Saber
To obtain this sword, in the World Of Ruin go to Firgao and into the dungeon where Edgar rejoins your party. Go into the room were all the thieves entered. At the center is a statue of armor. Approach to it and press X to get the Soul Saber. This is a great sword, as it deals damage by how much MP you used. It also refills you MP.
Get the Genji Glove early
When Bannon asks you to join the Returners, say "No" three times. One of the people inside will give you the Genji Glove.
Getting Raiden
To get Raiden you need Odin. Go in Edger's castle in the World Of Ruin and go underground. When the game states that you hit something, go and check. In the jail there will be an open door. Go through it and you enter a cave. After the cave you will get into the Ancient Castle. Enter the throne room, go to the right side of the throne, walk five steps down, and press X. When you do this go into the right room, and a new room will be there. Note: If you do this you wll lose Odin and gain Raiden.
Getting Gogo
In the World Of Ruin, go to the northeast triangle island. Bring strong characters. There you will meet a monster named Zoneeater. It uses Demi, but also uses an attack called "Engulf" that sucks a character into him. Allow him to use "Engulf" on all of your characters. The game will not end. Instead, you will end up in a cave. This cave has strong monsters and great treasures, such as the Genji Armor. Jump across the bridges and avoid the walking people to eventually reach the end. Walk through the door and you will see a covered-up person. Talk to him and he will join your party.
Getting Yeti
Go to Narshe in the World Of Ruin. Have Mog in your party. Then, go to the mountain where you first got Mog. You will see the frozen Esper from the start of the game. Use Fire attacks on him and defeat him. This is the esper Tritoch that teaches Fire 3, Ice 3, and Bolt 3. Then, go to where the Esper was located and slide down. You will be in a cave. Most of the chests are trapped, and only have a secret path to them -- do not touch them. At the end of the cave, go to the skull statue, and take the Esper. Yeti will attack you. Defeat him, and if you have Mog in your party, he will join.
Getting Odin Esper
Use the following trick to get the Odin Esper quickly, without getting into battles. After receiving the Airship in the World Of Ruins, go to Narshe. Go to where the Moogle Village is located. Talk to Mog and he will join the party. In the location where you found Mog, search the wall to retrieve the Moogle Charm (when equipped on Mog, you will fight no random encounters). Go to Figaro Castle and talk to the engineer to head back to the desert. When the castle is moving, you will suddenly stop and the engineer will mention something. Go to the prison cell with the door and go through. Have Mog in the party with the relic Moogle Charm equipped. Follow the path until you reach the Ancient Castle. Go to the throne room and search the statue to retrieve the Odin Esper. You will never encounter an enemy unless you open two chests that contain monsters. If this happens, just cast Vanish then Doom to dispose of them. This is an easy way to get Odin and learn the rare spell Meteor.
Economizer relic
This relic turns all MP used on any magic move to only 1 MP. You can only get it the second world, after Kefka blows up the world, above the Veldt (the place where you teach Gau new moves). It is a small forest patch on the island just north of the Vedlt Island. You will be close when Tyranos start attacking. Keep fighting them and every once and a while a monster called a Bracosaur will attack. Have Locke steal from it. If that was unsuccessful, kill it and hope that it appears after the battle.
Elixir
Go any town and check out the houses. Many houses have a grandfather clock. Walk up to the clock and press X. You will most likely receive an elixir. Note: This only works once per clock.
Easy Catrot battles
You will find a creature called the Cactrot in the desert southwest of Maranda. It only has 3 HP, an extremely high Evade. Equip your characters with a Sniper Sight and a Genji Glove to take off 2 HP every time it is attacked. This can also be helpful when you face a Catrot in the coliseum.
Cast Ultima five times for 1 MP
Equip the Economizer and Gem Box relics to allow you attack two times for 2 MP. Make sure you know the magic Quicke, then enter a battle. Cast Quicke followed by Ultima, then just Ultima four more times.
Throw anything twice
The following trick allows you to throw anything twice, even if you only have one of the item. Have Gogo mimic Shadow to throw the same item twice. Note. If you throw an item that you have more than one of, Gogo will use his own and you will lose two items instead of one.
Get Cyan in World Of Ruin
Go to the town of Zozo. Talk to the only man that is walking around (not jumping from building to building or laying down). He will give you an item. Then, go to the top of the building with the door that is rusted shut and use the item that the man gave you. It will open the rusted door, which leads to Mt. Zozo. There, you will get in a lot of fights and eventually meet up with Cyan.
Hear different music
Go to the bonus screen to hear a selection of music. Go back and forth from the bonus screen and the start up screen and each time a different selection of music will play.