Player Statistics and What They Mean
It can be difficult to determine the best gear for your character - especially when you may not understand what all the modifiers on it mean. Spirit? Agility? Strength? Which is more important depends heavily on your class and the role you're trying to play (druids, for example, can heal, do magic DPS, or do physical DPS - in cat or bear form - and different stats are important for each role). While there are few official numbers regarding what equals what, the player community has done a lot of research and speculation, giving us a pretty good idea as to what each means. (However, there may still be some inaccuracies - and if you think you see one, let me us know!) Read on for more detailed information.
Strength
Increases melee attack power
2AP per point for warriors, paladins, druids (all forms), and shamans
1AP per point for rogues and hunters
Increases the amount of damage blocked by a shield (for classes that can use shields)
Agility
Increases ranged attack power
2AP for hunters
Increases melee attack power
1AP per point for rogues and cat form druids
Increases armor
2 armor per point for all classes
Increases ranged/melee critical strike chance
The amount of agility needed varies for each class, ranging from 53 for hunters to 20 for warriors.
Increases your chance to dodge
Again, the needed amount of agility varies per class. Rogues get the most dodge benefit from agility.
Stamina
Increases your health
10 health per point for all classes
Intellect
Increases the rate at which you learn skills (weapon skills, trade skills, etc)
Increases your mana
15 mana per point for all classes with mana
Increases spell critical strike chance
While the assumed formula has always been 100 intellect per spell crit, recent posts by Tseric suggest that this is not the case, providing a number of 59.6 int per crit for mages.
Spirit
Increases health regeneration
Only works outside of combat
Exact formula unknown (though seems to be different for each class)
Increases mana regeneration
Spirit/4 13 for priests
Spirit/4 11 for mages, hunters
Spirit/4 8 for warlocks, paladins
Spirit/5 17 for shamans
Spirit/5 15 for druids
Mana will regenerate at any time (in or out of combat) when you're outside of the "5 second rule" - meaning you regenerate only if you have not cast a spell in the past 5 seconds. (This is timed from the end of the last spell cast.)