When I started doing research in how to gear up my Paladin I found that a lot of the gearing is the same as for my Warrior, for that reason this guide ended up looking a lot like my Warrior Pre-Kara guide. The most significant difference is that you're going to want to get some decent +Spell Damage. The best place to do this without sacrificing other stats is to put it on your sword. Since your sword does not need to have high damage (most of your threat is generated through Holy Spell Damage).

I try not to depend on dropped items, since they are undependable and there are usually other solutions. If you have an item drop that is comparable to the items that are recommended, consider it a bonus. If you're into collecting sets, one set that is particularly good for paladin tanking is the Righteous Armor set. It drops off the following bosses:

Breastplate of the Righteous from Warlord Kalithresh - Steamvault
Gauntlets of the Righteous from Warchief Kargath Bladefist - Shattered Halls
Helm of the Righteous from Pathaleon the Calculator - Mechanar
Legplates of the Righteous from Aeonus - Black Morass
Spaulders of the Righteous from Laj - Botanica

Crafted / Purchased Items
You can buy the following items from Blacksmiths or off the Auction House:

Head Felsteel Helm
Hands Felsteel Gloves
Legs Felsteel Leggings *Easily replacable by earning revered with Keeper's of Time for Timewarden's Leggings
Shield Shield of the Wayward Footmen

You can also buy from a Tailor or off the Auction House:

Back Cloak of Eternity

There are better options for each of the listed gear (see complete list below). But if you want to suit up quickly, buy these off the Auction House and throw some Solid Azure Moonstone or Solid Star of Elune into the sockets.

Netherstorm
WAIST Complete the Tempest Keep quest chain that starts in Area 52: Warp-Raider Nesaad. Eventually you will be sent to Botanica and Mechanar for pieces of the Arcatraz key. As a reward you'll receive this belt: Sha'tari Vindicator's Waistguard.