When you have determined which class or classes you'd like to play, look at the in-game help page for your specific class.  Let's take the CLERIC class as an example.

Help cleric provides the following information:

The cleric is a member of a religious order, but he is no mere priest. While he may not have as much fighting skill as a warrior, he is far from a noncombatant. The clerics of JediMUD, however, adhere to a strict religious belief that forbids them from wielding edged weapons such as swords. Most of the cleric's power lies in his faith in his deity, who grants him spells which do everything from healing his allies to smiting down his foes with holy flames. The primary statistic? for a cleric is WISDOM. Having a high wisdom will help to increase the effectiveness of his spells. Having a high STRENGTH and CONSTITUTION are also definite plusses for a cleric. A cleric can be of any alignment.

To create a new cleric, you'll want your  INTELLIGENCE and WISDOM to be optimally 18s.  When you create a new character, you won't be able to see your base WIS and INT stats until you reach level 5. (This was done to prevent players from using triggers to create low-to-perf characters automatically.)

Upon reaching level 5, examine your stats, and if you don't have 18s in your prime stats categories (INT and WIS) reroll your cleric at the Phrenologist (located in a shop in each of the main cites of Midgaard, New Thalos and Skara Brae.)  You get five free rerolls.  If you still don't have 18s in INT and WIS, you can buy rerolls  at 250K gold per re-roll, or, if you're a new player without lots of gold, delete the character and re-create, duplicating the process above.

It's important to start with 18 INT/18 WIS due to the additional spell bonus you'll get when spell-casting, as well as a 12% mana regen bonus.  If you're new to the game, you typically won't have high value equipment that provides sufficient mana regen bonus and you'll have to rely on your native INT/WIS stats to begin. 

High constitution (18 CON) will provide more hit point gain per level, too, so it is advisable to try to roll and re-roll for 18 CON as well (if you have either the gold or the patience).

Starting a Cleric as a Paladin or Anti-PaladinEdit

Some players have discovered that starting your mortal career as either a Paladin or Anti-Paladin, will give you higher STR, CON and WIS attributes to start, with a relatively lower INT stat.  If you can get STR at 18/50+, an 18 CON and an 18 WIS as a Paladin/Anti-Paladin, upon remort, you can add up to 3 stat points to your INT category to compensate.  Though this requires a remort to Cleric, you will get a much higher starting stat base for less gold and time!

Like all classes, the cleric can increase his skills by using the? PRACTICE command.