So patch 3.0.2 came out and you heard that Paladins are overpowered. Since there's a month to go before WotLK comes out you decided to test your skill at leveling the cockroaches of the WoW universe. Here's a brief primer to get you started down the road of the holy warrior.
Note: The following guide assumes that a leveling Paladin is Retribution spec. This is the fastest spec for leveling, although Protection can become viable at around level 40. For those of you planning on leveling as Holy, please reconsider.
Armor to look for:
Starting at level 1, Paladins can wear mail armor. Later, at level 40, they can train the ability to use plate armor. Because we are only considering an item's utility for leveling and not PvP or raid PvE, heavy armor can be very useful by reducing the amount of damage taken and, thus, downtime needed to heal/eat.
This is not to say that leather, or later on mail, armor is useless. The player must weigh the value to leveling speed of armor versus the potentially greater dps stats on a piece of leather armor. A prime example of this trade-off would be comparing the Blackened Defias Armor and the Phantom Armor. Both are of a similar iLevel and have similar stats. The main difference would be the 109 armor gained by wearing the mail armor versus the 1 strength and 3 agility gained from the leather armor.
Weapons to look for:
Due to the nature of Seal of Command's proc per minute system, and later on the nature of Crusader Strike, a slow two handed weapon, such as the Corpsemaker, is ideal for the leveling Paladin. The slower the better.
Stats to look for:
The stats needed for leveling are very simple, compounded by the fact that newer stats such as haste or armor penetration are rare until the BC raid scene. Even stats such as hit and crit rating are hard to come by until you enter BC leveling content. Thus, you only have to be on the lookout for a few, select stats.
Stamina - As a leveling stat, Stamina is useful for Paladins just as it is useful for all classes in that it will help you live if you pull to many mobs. However, because of the incredible resilience of Paladins and their propensity for surviving sticky situations via their bubble, stun, and healing, Stamina becomes useful, but not overly so.
Strength/Attack Power - The bread and butter stat of Paladin leveling. Take as much of this as you can get. Strength vs. attack power can be calculated as 1 strength = 2 attack power (assuming you do not have Divine Strength).
Agility/Crit - Because crit rating is rare until the BC leveling areas, agility will be a far more common statistic found that can be used to increase your chance to score a critical strike. While critical strikes can be very powerful, Strength/Attack Power remains a better stat if you need to choose between them.
Hit - Like crit rating, hit is rare until the BC leveling areas. Hit, however, is useful only up to 5% when fighting equal level mobs, so don't go out of your way to stack this.
Expertise - Also rare, but still findable on some items in the old world. Expertise is an excellent leveling statistic due to the fact that it reduces both dodges and parries, instead of just dodges in PvE raiding.
Talents distribution for leveling.