-While inside Kresselack's Tomb, past the first big door, will be a Skeletal Mage named Mytos. If you are polite to him and opt for a nonviolent solution, you will get extra experience points before the fight.
-To level up a character easily, have only one character and go through the first quests at the starting town. After that, save the character as an import. Start a new game and load the import. Do the same quests as if you were using a new character. It does more difficult to level up, but it is possible to get your character to level 22 before going to the next town.