When it comes to Retribution, there are most of the players out there who still do not know what the flux. So we here take this opportunity to make mention of it in detail so as to help more players understand.
   In raids, for Player vs. Environment Seal of the Martyr or Seal of Blood depend on your faction. Seal of Command is reserved for times when the kickback damage would kill you. For Burning Crusade veterans, for example, it would be Prince Malchezaar in Karazhan. For Wrath green hands if you see your HP dropping dangerously low more than once or twice in an encounter, switch to Command and play it safe. Dead players do zero DPS.
For Player vs. Environment solo or Player vs. Player, Seal of Command is your choice.
Retribution doesn't have a set rotation such as a Rogue or a Mage might. Retribution normal functioning is akin to a shadow Priest's priority skill system, keeping everything on cool-down as much as possible.
Hammer of Wrath is the most damage, hit it as soon as it comes up and keep doing so whenever possible, providing it doesn't interfere with Judgment. Judgment is a ton of damage and returns mana, keeping your resources flowing. Crusader Strike is more damage for less mana than Divine Storm, hence why it is ahead of Divine Storm. For Area of Effect situations, this priority ranking changes, the above is for single target DPS. For multi-target, emphasize Divine Storm and Consecration.
First and foremost, you should gear Strength, because it increases all of your DPS abilities and scales the best out of all stats for ret paladins. Stack as much as you can. For raiding, you want to aim to stack hit as well, to about 262 rating (which will yield 8% hit, the most needed for hitting a raid-level boss), and expertise to 26 skill to eliminate dodges. Past that, crit is great, and then haste and armor penetration can come as they may.
For the most part, both Glyph of Judgment and Glyph of Consecration are used for sure. For the third major glyph spot, take your pick of Glyph of Avenging Wrath, Glyph of Hammer of Wrath and Glyph of Crusader Strike. As long as you include Glyph of Sense Undead as one of them, it doesn't matter. We highly recommend using Glyph of Lay on Hands in one of your other minor slots.
And then you will get Enchant for Attack Point. Certain enchant like Icewalker to boots are exceptions but for the most part, spring for AP. AP to bracers and gloves, Arcanum of Torment, Icescale Leg Armor and so on.
About socketing the gear, Meta = Relentless Earthsiege Diamond. Past that, fulfill the meta requirements with orange/purple gems that contain strength, and then stack strength. If you don't have a bunch of bold red gems, you did it wrong. As of the latest version of this FAQ, the best gems you can use are the above meta, one Sovereign Twilight Opal for the blue requirement, one Inscribed Monarch Topaz, and as many Bold Scarlet Ruby as money can buy.
Note that the Meta gem recommendation above doesn't apply to Jewelcrafters. Their prismatic gems allow them to use a different Meta to greater effect. For further discussion, see my post on Meta gems.
It's not necessary to stack spell power/intellect, only stick to the melee DPS plate. On occasion, you can branch out into the Hunter mail or the Rogue leather. Don't you dare put on that elemental Shaman mail, we will find you and beat the sense back into you.
Whichever one has the higher DPS, unless there is a huge difference in damage range. If the DPS is the same, pick the one with the higher top damage. For example, The Jawbone has the same DPS and a higher top damage than Death's Bite, therefore pick The Jawbone if you're choosing between the two.
Running out of mana, make sure that you are using Divine Plea on every cool-down and your Judgments are not missing by having a good amount of +hit. Then you can make use of a mana potion and cut back on Consecration if you're spamming it. If you're running low on mana, you're doing something wrong. Parse your damage on an encounter with Recount, screenshot the skill split, and seek professional help.