Easy Experience Points:

If you want lots of easy EXP then just head for the Island Closest to Heaven or the Island Closest to Hell. These islands are also excellent for their abundance of draw points of rare and powerful magic, i.e. Ultima, Meteor, and Full-Life. Even though both places offer you a plenty of experience, the Island Closest to Hell has monsters with rarer/better items, more drawpoints, and even more experience and AP.

Easy AP:

For fast and easy AP, just go to Cactuar Island: a small island between the Centra and Esthar continents (note: click here to view a map.) Each Cactuar is worth 20 AP, and if you're lucky, you'll kill several of them per battle. Squall should at least be able to dispose of one per battle because of his 255% accuracy.

Buying Phoenix Pinions

50 Phoenix Downs = 1 Mega Phoenix

3 Mega Phoenixs = 1 Phoenix Pinion

Raising Characters Well:

This is the most important thing you can do to easily make your characters very powerful. Level up as little as possible until you get the Cactuar GF. When you get Cactuar, take the party members who aren't junctioned to Cactuar out of your party. Equip the person using Cactuar with Cactuar's bonus abilities and no other abilities. Then go to your favorite leveling up place. Once you're at LV 100, that character's stats will be very high. Then put one and only one other character into the party and do the same stuff as you did to the first character. Do this for all of your characters. Once they're all at LV 100, they will be extremely powerful.

Easy / Desperate Money:

If your really desperate for cash (like you have no gil and/or very little), you can sell the letter from Edea at a store. Then you can go get another from her and continue if you wish.
- Posted By SLeonhart49 -

Level 100 faster:

First, make sure that quistis has her Blue Magic: Degenerator and can use her limit break. Go to the Island Closest to Hell, and get into a battle. Have Squall and the other character attack, and have Quistis use Degenerator. If her limit break doesn't appear right away, keep pressing Circle until it does. The enemy will die instantly, giving you lots of experiance, fast.
- Posted By SLeonhart49 -

Raise Stats By Devouring:

You can raise some of your stats to full 255 by devouring certain enemies. Such high stats would make you virtually invincible. The following are enemies that you should devour to raise stats, and which statistic they raise and by how much.

NAME	STATS
T-Rexaur	Strength + 1
Ruby Dragon	HP + 10
Adamantoise	Vitality + 1
Malboro	Spirit + 1
Behemoth	Magic + 1
Pupu	Speed + 1
Rinoa	HP + 10
Catuar	Full health restore

NOTE: You can only fight Pupu once, so its better off that you don't Devour him but rather get his rare card. Also, although you can devour Rinoa, this will cause you to lose the game, making it pointless, so just don't devour her.