-To get easy levels, find an area in the game with a rare monster (they have red circles around them). If they are near a door, kill the monster and quickly go through the door. If there is another rare monster nearby, also kill that one before going back through the door where you killed the first monster. It should have spawned again. Repeat this process to gain plenty of expeirence.
-When you first begin, kill all the monsters as you usually would and exit the tavern. After editing, kill all the monsters up to the Academy without getting too close to the top of the Academy or else the game will start your next quest. Run back down to the tavern and enter it to find that the monsters have respawned. Kill them again for more experience. Repeat this and you should get a decent amount of experience until you are at about level 30. This works especially well for Knights to do their Aura of Valor.
-Note: Two PSPs with the game is required for this trick. You also need a character over level 40. Have the person with the character over level 40 invite a lower level character into his game for Multiplayer mode. The lower level character should be below level 30. Then, have the lower level character stand back and hit them with arrows (if possible) to get experience points, even though he is not fighting. The lower the level, the better this will work.