***Pre-Scriptum: The information in this is found generally in the game mechanics, as well as information available to the public from forums pertaining to said game mechanics and computing programs related to the World of Warcraft*** This is my attempt to help prevent alot of repetative posts, and generally lend a hand to informing visitors to Ret Paladin mechanics. Thank you in advance!
This post is intended to help those not familiar with alot of the Retribution Paladin mechanics to get a fairly simple overview
Spec
5/5/53 is the spec
Here's the link: http://www.wowhead.com/talent#sVZVZVfbt0IuhdIfsu:0GZm
Just cut and paste it. It leaves a few points open for you to choose something extra...
***Note: The Link has Glyphs Already in there for You***
Pursuit of Justice
You arent facing alot of disarms on a boss fight, but movement speed increase to the boss is important, because it's more time to dps. This also has utility in pvp (as does Eye for an Eye, Divine Purpose, and Unyielding Faith).
Vindication
This talent will affect bosses. It's a nice raid utility talent because it'll save your other tanks the other tanks and dps a cooldown to use the same ability that you get passively.
Divinity
You shouldnt be taking all that much damage, and the damage you do take wont need the extra 5% (which is relatively tiny and probably means more overhealing)
Divine Intellect
Generally, you'll be picking up this talent on the way to Aura Mastery. And, more intellect means more mana and more crit which means more pew pew!
Healing Light
Art of War will give you that free Flash Heal, but you're better off using the free exorcism for damage and getting the heals from Divine Storm.
Glyphs
Glyph of Seal of Command
This isnt recommended, because you'll get alot of mana back from Divine Plea, Judgement of Wisdom, and Judgements of the Wise.
Glyph of Exorcism
Replace the suggested Glyph of Seal of Vengeance, once you reach the Expertise cap without it. The extra Expertise beyond the cap will just be a waste.
Stats
Hit: you'll need 8%, or 263 hit rating, 7% if you're a Draenei. This is the melee cap for you. To reach the spell hit cap, you'd need 17% hit rating (16% if you're a Draenei). The spell hit cap is super incredibly unrealistic to try and achieve. You'd be sacrificing far too many stats to try and reach it. Good news though! Having that Boomkin or Shadow Priest or Unholy DK in your raid will benefit your spell hit as well as theirs!
Expertise: you'll need 6.5% to cap it, or 214 expertise rating (note, though, that being a human or dwarf and using certain weapons can help you get capped faster). On your character screen, this will also appear as 26 (for your Mainhand)
Strength: give you all your Attack Power. it's the next most important stat after you're hit capped.
Crit: this is typcially the next most important stat after Hit and Strength because it triggers your free Exorcism
Armor Pen: You dont want this. This stat makes your physical damage better against heavily armored targets. Magical damage always ignores 100% armor. Two-Thirds of a Ret Paladin's damage output is magical, so the vast majority of your damage does not benefit from ArPen. You're significantly better off with Strength, Crit, and Attack Power based gems/enchants/trinkets. You do not want Armor Penetration.
Haste: wont kill your dps to have it, but dont go out of your way to get this over other stats like Strength
Attack Power: you'll get it from Strength.
Agility: much better than ArPen but (with only a couple exceptions) less useful as Strength, Expertise, and Crit.
Armor: like 99% of the time you'll wear plate. You want plate for its Strength, but since Paladins don't get nifty talents to up their Attack Power as a function of their Armor Value (i.e. DK and Warriors), it so happens that there are a handful of leather AP items that out-perform their strength-based slot item of the same value. =)
Gems
Meta: Relentless (+21 Agil and +3% crit dmg), hands down; the Chaotic (+21 Crit and +3% Crit Dmg) would be much better except that you would be wasting gem slots trying to get two blue gems to activate it.
Red: Bold (+20 Str)
Yellow: Inscribed (+10 Str and +10 Crit), use this only in yellow spaces if the socket bonus nets more Str or Attack Power, otherwise use all Red
Blue: Nightmare Tear (obviously you can only get just one, so put it in a good slot!)
Priority (not a rotation)
Here's the good(?) news... Ret doesnt really have a rotation or a priority. Because of how the Ret mechanics function, every ability goes on cooldown for a certain amount of time making each subsequent ability comes off cooldown alone. (otherwise stated, whatever the next ability is that comes up... you use). This makes Ret surprisingly easy. Given this... a very weak sense of priority means:
1 ) Judge Wisdom (if you have a holy paladin they will Judge Light. If you have another ret paladin, then coordinate who will do Light and who will do Wis)
2 ) Hammer of Wrath (if under 20%)
3 ) Exorcism (only if it's instant cast from Art of War)
4 ) Divine Storm
5 ) Crusader Strike
6 ) Consecrate
At this point, you will only be able to cast abilities as they come off cooldown (or proc, in the case of Exorcism)
***As a Post-Scriptum, here, there are some tier set bonuses which will skew this priority slightly, but that's for a (co)responding post***