7. You can gain a level every two minutes
A great way to level up in general is to head to one of the areas where the enemies respawn every time you enter. The garden in Mickey's Castle is a goodspot to campearly in the game, for example. There's at least one solid location in The Land of Dragons too.
But the Mother Lode for leveling up appears later in the game. After your second trip to the Pride Lands, you can head to Pride Rock with a Magic level of at least 53 and farm the enemies called Rapid Thrusters. They'll appear in swarms. Turn off all of Goofy and Donald's healing abilities, and take damage yourself until that annoying "low health" siren starts. If you have them, equip the Experience Boost ability and swing the Gullwing keyblade. Then, use Magnega and Thundaga to wipe out all of the monsters flying about - the swarm will reappear every time you leave the area and return. Instant kills andthe resultant fountains ofexperience points make it possible to gain a level every 90 to 180 seconds.