A couple of Helpful Tankadin Macros gotten from Tankadin.com

Ok, paladin tanks have 5 moves that are routinely used for threat.

When you add in

1. 3 moves that have 6 second cooldowns
2. 2 moves that have 8 second cooldowns (with global cooldowns, its referred to as a 9 second cooldown)

The highest threat rotation possible comes from using a 6s move, then a 9s. so it looks like "6 9 6 9 6" start over.

One Macro is:  

1.  /castsequence reset=6 Hammer of the Righteous, Shield of Righteousness

The other macro that you'll use is

1. /castsequence reset=9 Consecration, Holy Shield, Judgement of Light
2. /castsequence reset=9 Consecration, Holy Shield, Judgement of Wisdom

I have them set to two keys w/ PageUp, and PageDown keybound to them. The second macro, I use the one with wisdom in heroics or situations where I'm not taking as much damage and need more mana than is provided by my Spiritual Attunement talent. Use the Judgement of Light for raids or high incoming damage scenarios.

It is easier to just hit PgUp, PgDn, PgUp, PgDn, PgUp, PgDn, PgUp, PgDn..... ad infinitum.

I however keep the skills themselves on my bars incase your in situations where you need irregular sequences of the rotation... like just needing consecrate and hammer alot.... like Halls of Stone.

Retribution Paladin

Maximize your DPS

Good dps warriors and rogues will dual wield. But as a paladin, the only way to get your dps on top is to get a high dps 2-handed weapon. I prefer using a 2H sword but 2H maces do as good. And since two-handed weapons don't hit as fast as one-handed do, your holy spells will become your best friends.

Soloing or with a group with no healer

Holy spells rotation : Retribution aura / (greater) blessing of kings / Seal of command / Judgment of light / Crusader strike / Divine storm / then repeat from judgment of light.

Grouping with a healer

Holy spells rotation : Retribution aura or Devotion aura for the tank / (greater) blessing of kings / Seal of blood(because it does more damage but you lose HP) / Judgment of light / Crusader strike / Divine storm / then repeat from judgment of light.

Don't forget to use Consecration everytime it's up (be careful not to hit CC'd target e.g. sheeped, sapped, repented)

Talents

http://www.worldofwarcraft.com/info/classes/paladin/talents.html?tal=000000000000000000000000001150000000000000000000000342322512233312322130231351

This is my talent tree but it's not the perfect model just as long as you have Divine strenght, Blessing of kings, Seal of command, Conviction, Vengeance, Crusader strike and Divine storm maxed out.

It's always a good thing to have repentance too. Your party will be glad to have you with them since this spell can CC demons, dragonkins, giants, humanoids and undead.

Stats

(most important to the top/less important to to bottom)

+strenght

+attack power

+crit chance

+stamina

+hit rating

+agility

+intellect +expertise +spell power

If you think I forgot something, please feel free to tell me and I'll add it.

So that was a large overview of being a good ret pally there sure is more stuff to know but those are more the things you'll notice by getting the hang of it and of course by your play style.

Have a good time Dps'ing :D