In order to level up, a character must gain 1000 EXP. The amount of EXP that a given enemy gives when defeated goes down as the character's level goes up, so an Imperial Commander will give over 500 EXP to a low-level character, but only 3 EXP to a high-level one.
Magic, instead of costing Magic Points like it does in most games, costs Hit Points (HP). Therefore, although magic is powerful, it must be used with caution: it is possible to K.O. a character by casting a spell when they are low on HP, and at low levels of the Magic Focus, a character will use more HP up on the Heill spell than they will heal.
In combat, meditate whenever you can, because it gives you 100 HP and also more damage in your magic or in your weapons against the enemy in the next turn.
You can choose the Focus of a given character, i.e. what they will gain levels and abilities in.
If characters are assigned to Magic, the amount of HP those characters use for spells will go down, and the power of the spells will go up. The player will also be able to read "magic books" found in different locations. To read one of these books one of the characters players must be a certain level or above it. By reading a magic book you learn one new spell.
If characters are assigned to Herbal, they will be able to pick higher levels of Herbs and make more powerful Potions, like health potions and salts, used heal and reanimate characters who died in combat (they will have 1 HP after the battle is over and they can fight in the next one to).
If characters are assigned to Weapon, they will gain strength in non-bow weapons and also earn special attacks. In addition, they will be able to challenge people in cities to battles that would not otherwise be available (and give prizes if won). In those combats, only the member with the highest Weapon level will fight, but they all get experience.
If characters are assigned to Endurance, they will gain the ability to move large objects. The player will be also able to break crates which can hide weapons, magic books or even potions. Also, if you have your Endurance in a high level, the character will receive life in battle, after his turn passes (meditate when you have your life low and having a high level of Endurance helps getting it back).
If characters are assigned to Hunting, they will gain strength with and special attacks for Bow weapons, and will also be able to follow 'tracks' in dungeons. These 'tracks', when followed, often lead to great treasures.