Meditate

Meditation will substantially increase the rate at which your character regenerates mana. This skill is trainable by all classes that have mana. To activate the meditate skill, simply sit down. This is also how you raise the skill - by simply sitting. You must train one point in this skill at the appropriate level (level 8 for Wis casters, level 4 for Int caster, level 12 for hybrids). The higher their meditate skill, the more mana per tick your character will regenerate.

If your character is on the hate list of any MOBs, then their mana regeneration will be halved.

Also, in order for your meditate skill to actually increase you must have less than full mana, meaning, it actually has to be working.

So you cant just let your character sit overnight and expect full meditate skill in the morning.