Each class in this game has a different way of playing, some dramatically so, others reasonably similar. You will always want to find the best way to be a member of the class you have chosen. Before you choose though, you should think about what suits your personality. Do you like to skulk around in the dark? Have you religious notions? Do you want to walk around in a big bright suit of armour for all the world to see? Or are you more of a scholar, leaning over books and finding out secrets of power thought lost long ago?

Here's a basic description of each class:

Fighter: The Fighter has access to all armor and weapons. Also the Fighter's "Power Move" is a powerful attack which is the full Attack Power (AP) of the Fighter. Fighters can get all weapons and armor.

Mage: Physically the weakest of all the classes and also most limited in weapons and armor the Mage more than makes up for this at high levels with powerful magic which can do more damage than even the strongest Fighter. Mages can only use Staff and Dagger weapons.

Priest: These holy warriors are a bit of both Fighter and Mage. The Priest has access to stronger weapons and armor than the Mage and has defensive and healing spells. The Priest also can call upon the power of the Gods to give them strength to defeat their enemies (The Priest's "Power Move" is Prayer which heals the Priest and damages their enemy). Priests can use Staff, Dagger, and Mace weapons.

Thief: The Thief has access to less weapons and armor than the Fighter, but can get better armor and weapons than the other two classes. The Thief's "Power Move" is Steal, which lets the Thief get extra experience and gold from enemies in the "Great Forest". Thief can use Staff, Dagger, Mace, and Swords.

I won't go into why I believe that the fighting class is called Fighters and not Warriors, seeing that Warriors are honourable. But my perception is a bit coloured seeing I play a mage.