The obvious pally buffs (speced means the person using it should have the talents that amplify it):
-Righteous Fury (speced)
-G Blessing of Might (speced)
-G Blessing of Wisdom
-G Blessing of Kings
-Retribution Aura (speced)
-Devotion Aura (speced) or Crusader Aura when mounted
-Frost Resistance Aura or Shadow Resistance Aura
-Fire Resistance Aura
-Sense Undead (Glyphed)

IMPORTANT CAVEAT:
One thing I've noticed with pallies is that they have several talents that amplify the power of multiple auras. It may seem like a good idea to split these talents between pallies - it isn't. You have to make sure that you put all those talents on the same paladin and that he activates his aura last. Failure to do so will mean that another pally's unbuffed or partially buffed aura will overwrite the bonus effects of the previous pally. The talents I'm talking about: Improved Devotion Aura, Sanctified Retribution, Swift Retribution. Get all these on your devotion aura guy and then get Sanctified Retribution also on your Retribution Aura guy.

-Use all 3 different judgements. Double up on judgement of light, it's the most important.
-Use Seal of Righteousness and get as many points in the holy talent that improves it as you can. I was able to get 3 points in it. Use a Seal of Command build only when you're in full relentless.
-Make sure you have 2/2 Divine Guardian on each paly.
-Use Sacred Shield on all your pallies (just self cast). If you're really good switch it off one pally to your DK when you see him being focused or if you're in PvE.
-As soon as you start taking damage pop divine shield and Divine Sacrifice on one pally. Wait 10 seconds (or if you see it mass dispelled) and pop it on the next pally. You'll have a long period of very high group damage reduction without sacrificing much DPS. DONT USE WINGS until after this is used up.

-In PvP you need to be able to throw massive heals at single targets. You need FoL with a /stopcasting at the end of it in round robin with a seperate button/macro for each member of your team as the target. You can make another similar macro for exorcism but chances are you wont want to both with this in arenas. You'll be healing.

-You NEED 5 cleanse macros in similar fashion to the FoL macros. If you're not cleansing your guys then you're not playing paladins.


-Each pally needs a
/cast [target=arena#] Repentance
and
/cast [target=arena#] Hammer of Justice

Range is low and you must be facing for these to work so they wont often work but spamming them can prove effective in many situations to lock down seperate individuals.

-Use Hammer of Wrath on low targets
-Spam Crusader Strike (get the frost emblem libram for this) and Divine Storm when in range
-Use your racials
-Use Concecration often in PvE and if you happen to feel like it in PvP. Sometimes it'll just break your repents and isn't worth it
-Spam hand of reckoning on PvE trash for a big DPS boost
-Consider using hand of sacrifice/hand of protection the same way as cleanse, very difficult though



DK Stuff
-Horn of Winter
-Path of Frost (can eat a dispel.. maybe I dunno I use it)
-Abomination's Might (speced - use a deathstrike immediately to proc this)
-Improved Icy Talons (speced - use a speced chains of ice immediately to proc this)

In the heat of PvP Arena battle you're going to be doing a lot of death strikes and a lot of death coils. Chains of ice and death grip is also your best friend. Save death grip for a secondary target and pull him into the AoE shitstorm you're throwing on somebody else. I still use all 3 stances and can't decide which I like best. The run speed and global reduction from unholy is great, damage reduction from frost is good and the extra damage + healing (if speced) blood is great.

You all know about interact with target, I spam this on my main guy too often. It allows me to focus on unit frames and ensure that the person I'm DPSing is a good choice. If you waste time DPSing a divine shield or hand of protection, or some other high damage reduction ability target then you will lose. Get an addon that will alert you to buffs your target may have. Don't DPS these:
Divine Shield,Ice Block,Dispersion,Hand of Protection,Divine Shield,Deterrence
and don't DPS these unless they're near death:
Divine Protection,Pain Suppression,Shamanistic Rage,Evasion,Anti-Magic Shell