Hint:
In the beginning of the game you are on destiny islands. When you see a thunder storm and run outside there will be heartless. Do not try to attack them they will not go away. (your sword is too weak) Instead go in the shack and across the bridge there you will recieve your keyblade. (this will help you not lose your life so you can defeat the heartless later and take on the big black thing)

Hint:
With the white mushrooms, in order to get the spell arts, you must cast a certain magic 3 times with the same magic however they do not have to be in a row so wait for the mushrooms to move into the same pose.

Poses/Magic:
Shivering/Fire magic
Squatting or sweating/Blizzard magic
Light above head/Thunder magic
Spins/Aero magic
Floats off the ground/Gravity magic
Falls on the ground/Cure magic
Stops completely/Stop magic

Hint:
If you need mystery goo and your not very good with the rare truffles (which you have to knock into the air) the white mushrooms drop mystery goo along with the spell arts.

Beat Cerbrus:
When fighting cerbrus strike his middle head but from underneith it, you can stand in front of is chest or under it's middle head and attack it very easily.

Beat Cerbrus, alternate way:
Get potions for you, Donald and Goofy. Hide under him. When he goes to attack, he will have his left leg down. When he has his left leg down jump on the leg, then climb on his back. DO NOT GIVE DONALD OR GOOFEY POTIONS! P.S. When he jumps up, there is nothing that you can do except jump off of it!

Easy mystery goo and items:
Go to halloween town, and go to the bridge area. There might be rare truffles there. If there are, go down into the water, and go to the far right side of the screen. There should be one there. Cast aeroga or aeroa and knock it over to one of the hills. Just sit there while the sheild hits it up in the air, and recast aeroa or aeroga until you have hit it in the air 100 times.

Misc. hints:
The enemies in the colosseum will not drop items so don't bother trying

During the fight with Riku 2 at Hollow Bastion, use the Olympia keyblade for some reason this makes the figt easier

While fighting Cerberus don't take him head on its suicide instead lock on to a side head and show him what the keyblade's made for

While fighting the ice titan you must hit the shards he spits at you back at him however if you use aero magic the chunks get huge and impossible to hit back at him

While fighting the dragon at hollow bastion use the beast instead of goofy, abilities must at least be strike raid and ars arcanum then cast tinker bell, customize your slots with aero magic and cure magic, jump on the back of the dragon (by way of the tail) and stand at the bease of the neck, use strike raid, also have many ethers for quick mp recovery.

In the beginning of the game you are on destiny islands, to level up easily fight wakka and knock the blitzball back at him this give you a tech pt and gets you closer to leveling up.

At the beginning of the game you are faced with some choices, picking the sword and sacrificing the staff you are improving your strength but depleteing your mp count. Sheid/Defense; Staff/Magic; Sword/Strength

The questions you are asked the first answers make you level up at a fast pace the second answers medium and the third slow. For instance a being the first a makes you level up fastest. It is done by majority so the most you pick thats what your gonna get.
 

Hint:
When you fight the dragon in hollow bastion, there is a root along the wall that you can hide behind, it will block you from almost all of the dragons attacks, so let your party members do all the work and then just come back to finish it off.

Hit boxes:
When you go to Olympia and you have to destroy the boxes. Do not lock on to any of the boxes (this wil help) hit them in the middle if the are in a bunch. This way you will finish faster and then you can move on to defeating Cerberas.

Defeat Ceberus:
To defeat Ceberus in the Colliseum follow my guide:
1. Attack him only from one of the side heads, do not attack him in the middle of the the three heads because that make you vulnerable to the side head's attacks.You only have to take out one head and then he is dead!

2. When he walks around the Colliseum follow him from behind, because he can attack you from the front.

3. When stands on his hind legs get ready to jump because when he throws himself to the ground a vibration of some sort glides over the Colliseum, the vibration is visible, so when you see it come close to you jump fowards, this way you will avoid the vibrations, but do not jump to early, because you could get hurt.

4. When he spits out fireballs they follow you. Run away from them in a zig-zag pattern and they will eventually dissepear.

5. When you see his paw lift into the air and then come back down a purple and black pool will appear under his paw, right when you first see the pool run everywhere you can in the Colliseum, because the purple and black pools start to appear all over the place.

If you follow these steps carefully you can beat Cerberus.
Hades Cup:
When trying to beat the Hades cup in the Leon and Cloud battle, kill Cloud first using the Divin Rose blade.

Find the Keyblade Oblivion:
To find the Keyblade Oblivion, before your battle with Riku2 in Hollow Bastion, jump up to the ledge on the opposite side to the portal. One chest has puppies, the chest directly opposite the portal holds Oblivion (str +10 MP -2).

Easy Level up

In the beginning of Kingdom Hearts while you are on the small island it is easier to level up fighting the kid that looks like Tidus. All you have to do is run away from him until he runs towards you. Then time your attack and hit when he hits, it should give you two points for each and in two hours of that on Expert I already was level 15.

Easy mystery goos:
Neverland has rare truffles. Go to the ships deck if there are none go through the bottom door on the deck. (not the one with the crossbone face) You will see a hole in the corner of the room. Go down it and then back up to the deck. Repeat until you find a whole bunch of Rare Truffles. Make sure you have at least one treasure magnet on. Cast your air magic and start flying a little off the ground then target the poor mushroom for some bashing when one jumps hit it out to the sea (yes out to the sea) this will avoid those stupid wooden posts on the ship from getting in your way and screwing you up. Now time your hits and continue popping it in the air I easily hit it 50 times the only time you will have to adjust is when your Aero magic stops working you'll have to attack a little faster.

Defeat Sephirof:
To Defeat Sephirof (the Platinum Match in the Coliseum), you will need to be at least be lvl 88 (recomended) with the keblade Oblivian or better. During the battle, you will have to hit him many times before the damage starts to get taken off his life bar. once you have got rid of about 1 and a half life bars he will do a move where he takes you down to 1 hp and 0 mp, so act fast and have MEGAELIXERS, (THIS FULLY RESTORES HP AND MP!) so equip as many as you can to save yourself from that magic, then show him what you are made of.

Defeat Cerberus:
When your against cerberus go to his hind leg and when he lowers them jump on his heel then jump on his back. It makes it alot simpler to defeat him, it worked for me.
 

Hint:
After you beat hollow bastian then you can fight the secret bosses. One of these is in agrabah. Go to aladdins house and the carpet should be dancing around, talk to him and when they ask you a question say yes. Then you should have to fight a secret boss. Once you start fighting him, you will not be able to use magic. So you have to destroy the two balls in his hand. After you destroy the two balls, you can hurt him. Then he will jump back up and you can use magic again. He will have a shield around him that you must destroy. The best way to destroy it is to run up to him and use thundera (or thundaga) on him. After you destroy his shield you have to reapeat it, except this time he will fly up in the air and spin around. The only way to dodge this is to dodge roll under him. Keep repeating this and you should win.

Easier fights:
Summon Tinker Bell in your fights. You can get her after beating Captain Hook, then sealing the keyhole at Big Ben. She always heals the party, and so you never die.

Easier Ceberus, Behemoth, Cloud and Squall, Hades, Rock Titan, and Ice Titan Defeat:
When you fight them make sure you have lots of MP, because you only have to use graviga spells, sometimes it kills them directly.

Getting the Ultima Weapon:
The Ultima weapon is Sora's best keyblade, this is the list of items that you need to synthesize to make it. You need 5 Lucid gems, 5 power gems, 5 thunder gems, 3 mystery goos and 3 gales. (Note: you must use trinity in the accessory shop in Traverse town that brings you to the synthesizing shop)