This technique works if you have the Gullwings' Keyblade. Head to the top of Pride Rock, where you can fight Thruster enemies. Have the Gullwings' Keyblade and any other experience boosting items equipped, turning off and/or removing any items or abilities that will automatically heal you.

Allow the Thrusters to attack you until you start flashing, indicating your health is low. At that point, start attacking. While these foes will normally give you about 50 experience points per kill, when you're critical, they'll give 170 experience points per kill.