Every paladin must eventually admit that it is very hard for them to be an offensive character. Nearly all of our abilities are centered around us being a defensive support class with nearly no abilities that up our damage. Warriors, hunters and rouges will always be able to out DPS you but if you know what you are doing you can get pretty close.
The first thing you must know about fighting as a paladin is that your damage will only partly come from melee. We have nearly no abilities that increase our damage like a warriors Execute or a rouges Ambush. They rely exclusively on increasing their physical damage. So in order for us to actually be able to beat things we supplement our low physical damage by dealing additional holy damage. Holy damage can’t be resisted like magic or reduced by armor like physical damage so it is a solid guarantied amount of damage that builds up over time. Primarily you will deal holy damage in three ways. Seals, judgments and set of unique spells.
Seals And Judgments.
Your first and best way to increase your DPS is with a Seal. Seals are short thirty second buffs that will directly impact your melee strikes. Each one has a unique ability and truly shine when you combine them with a judgment. While you have a seal active you can use your Judgment ability to remove your buff and inflict either damage or a debuff to an enemy. After you have used a judgment you can immediately cast another seal on yourself. Some seals benefit greatly from the debuffs of judgments so in most of your fights you will be juggling combos to maximize your damage.
Seal and Judgment of Righteousness.
This seal will add an additional bit of holy damage to each of your melee strikes. The slower your weapon the more damage it will deal. It is almost never resisted so it causes steady damage over time, but it is one of the weakest seals in terms of increasing your DPS.

Judging an enemy for Righteousness will deal an instant burst of holy damage. This is our only method of controlled burst damage so it is excellent for finishing off an enemy. Many monsters run away when they have low health and we have no solid ranged

abilities to send after them. So you can use a judgment of righteousness to finish them off before they flee. There is also a technique known as righteousness juggling where you will judge an enemy and then use seal of righteousness while you wait the ten seconds for your Judgment ability to cool down. Once it is ready you judge the enemy again for another burst of damage.
There are several way to improve your usage of Righteousness. By far the most popular is to first use the debuff from Judgment of the Crusader. It will directly increase any holy damage done against the target by a set amount. Righteousness is also the preferred seal for tanks because it is a constant source of holy damage.
Seal and Judgment of the Crusader.
Seal of the crusader is a unique seal since it has three effects. First, it directly increases your attack power by a set amount. Second, it lower the time it takes to swing your weapon by forty percent. But its final effect is to lower you damage by a certain amount. This last aspect is very confusing but there is a reason. Damage is decided by how long it takes to swing your weapon so when your swing time goes down your damage output has to go down as well to match. Your DPS will still remain the same, but you will get a boost to your attack power. The lowering of your swing time and damage is rather confusing but it is actually a useful benefit in certain situation. Faster weapons are best used against enemies that cast magic since your hits will interrupt them and increase their casting time. This is a rather small benefit that is rarely worth the loss of a more powerful seal so many people rarely use Seal of the Crusader unless they want a direct increase to their attack power.
Judgment of the Crusader is much better then its seal. It acts as a debuff that makes the enemy vulnerable to holy damage and increases the amount it will take up to a certain amount. This is one of the only debuffs in the game that increases holy damage. If you are soloing a hard monster then it is usually best to enter battle with Seal of the Crusader and immediately judge the enemy. With the debuff up you can then use a different seal that deals holy damage like Righteousness or Command to increase you damage substantially.
Seal and Judgment of Command

This is a the hardest hitting of your seals and the absolutely best way to increase your DPS as a paladin. Seal of Command has a chance on a successful melee hit to deal extra holy damage equal to 70 percent of your weapons average damage. This means that

the higher your weapons damage, the more extra damage you will deal. Command also has a mechanic that will let it proc seven times per minute. If you have a fast weapon you will swing more times per minute and have fewer chances of it triggering a proc. (1.50 speed = 17% chance of a Command proc.) But if you have a slow weapon you will swing fewer times and have a higher chance. (3.00 speed = 35% chance of a Command proc.) These two factors mean that the best weapon to use when using Command is the hardest hitting two handed weapon you can find.
Judging Command will deal a burst of holy damage similar to Judgment of Righteousness. Normally it will hit for about the same damage as Righteousness, but if the target is stunned or incapacitated it deals nearly twice as much. This means that you will want to use your judgment only when the target is stunned. Fortunately you have abilities like Hammer of Justice to stun the enemy.
Seal And Judgment Of Light And Wisdom
These two seals are almost exactly alike so I'll talk about them at the same time. When you have one of these seals active your melee hits will have a chance to either heal you or give you mana. If you judge an enemy for either Light or Wisdom, each of your strikes against them will also have a chance to give you health or mana. The seal effect is primarily used by protection paladins to keep their health up. But the judgment effect applies to everyone else hitting your target and is useful in raids and groups.
Seal And Judgement Of Justice

This seal is somewhat misunderstood and can be very useful when used correctly. The seal effect is not terribly useful in PVE compared to other ones like Command or Righteousness, but it is somewhat more useful in PVP. The real strength of this seal is its judgment effect. It also is at it's strongest when used in PVP since it limits an enemy's movement speed to just one hundred percent. This way they can't escape with

abilities like sprint or with speed boosting items. Since paladins can only fight effectively in melee range it can be very helpful for slowing down a runner.
Seal Of Vengeance
This seal is primarily used for protection specced paladins. At the higher levels and with enough spell damage it can cause more holy damage then Seal of Righteousness. Making it an excellent seal for tanking. It is also an awesome damage dealing seal when AE grinding. Every time you attack you have a chance of debuffing your opponent with a DoT that deals holy damage. On it's own this isn't terribly useful since you will rarely swing fast enough to make it worth while. But when combined with the Reckoning talent in the protection tree you can apply the dot effect very quickly thanks to your extra swings. Once you have five stacked up you can judge the enemy for an extra burst of holy damage. This is an alliance only spell though so you are out of luck if you play a blood elf.
Seal Of Blood
This is essentially a fusion of Seal of Righteousness and Seal of Command, with a little health loss on the side. It has very limited uses in PVE since you will be constantly losing health and need someone to heal you. Its greatest strength is in PVP for some additional burst damage. If you have a dedicated healer helping you and a very hard hitting weapon it is not a bad choice, especially against high armor classes because the extra holy damage won't be reduced.
Buffing.

One of the great strengths of a paladin is their ability to buff their allies. First are your Blessing buffs. You can only put one of your buffs on a target at a time so you need to pick the one that will help that class the most. Melee benefits he most from Blessing or Might, Kings and sometimes Salvation. Magic classes will usually want Blessing of Wisdom and Salvation as well since they have such low survivability. Other blessings are more specialized. Blessing of Light and Sanctuary

are best used on tanks and players that require a lot of healing. And Blessing of Freedom and Blessing of Protection are mostly used to save an ally in PVP.
The second best way to buff yourself with one of your auras. These apply to all of the people in your party whenever they are close to you so you need to balance it among the different classes. If you are in the tanks group you would probably want to use Devotion Aura for the extra armor. But if you are in a caster group you would probably want to use concentration Aura. When in a group though most people rely on their resistance auras to protect against fire, frost and shadow damage. Others Retribution aura arn't useful in PVE groups, but very useful in PVP.
Buffing yourself
Finally, when playing in a group you will want to invest in some consumable buffs like potions or scrolls. When using these you will want to focus on one aspect of play at a time instead of increasing all of your stats evenly. If you are healing invest in mana and healing potions. If you are tanking look for items that increase your armor and damage mitigation. And if you plan to DPS focus on your strength, agility and stamina. There are also expensive potions that increase several stats at once like crit chance and agility. These are too costly to use every day though but can be worth it in special situations like soloing dungeons. A cheaper alternative is to invest in sharpening stones (or weight stones for mace users) or magic oils. Stones increase your weapons damage and oils will increase your magic damage but your can only have one. Stones are usually cheaper then oils but only deal a little bit of extra damage on your weapon hits. Wizard oils will increase your holy damage a little bit, but they are much more expensive.