I'd be glad to walk you through prot tanking in-game if you have any questions. I'll outline the basics here. You can see my current build on the armory, look up Redletters (I'm the only 80 with that name).
Here's the link:
http://www.wowarmory.com/character-talents.xml?r=Stonemaul&cn=Redletters&gn=Redeemed
The build I have has the basic prot talents that every tank should have, coupled with some off-talents in the other two trees. Another acceptable build is to keep my prot tree as-is, and spec deeper into the Ret tree for Crusade, which increases all damage, and therefore threat.
Right now, I've taken those points and used them in the Holy tree, getting Seals of the Pure (also increases damage/threat), going down far enough to get Improved Lay on Hands (reduces damage after casting it, and reduces the cd by four minutes).
Both of these builds are considered acceptable prot builds, and you should have no trouble with either of them, it's your preference really. I specd for Crusade while I was running heroics, but now that I'm moving toward raiding, with longer boss fights, I went for Seals of the Pure and Imp LOH.
With the LOH build, or with any build actually, you'll only want to be putting one point into Improved Judgments. The reason for this is because with the spell rotation you'll be using at 80, a 2-second reduction in cd is useless; the 1-second reduction works just fine.
The rotation I'm talking about is known as the 96969 rotation. This idea is taken from maintankadin.com. Basically, it works like this:
You have three abilities that have a 9-ish second cd, and two abilities that have a 6-ish second cd:
9-ish second cds: Judgment, Consecration, Holy Shield
6-ish second cds: Hammer of the Righteous, shield bash (drawing a blank on the name right now)
You'll basically be rotating these (rotations can differ based on the fight). I'll usually hit Holy Shield(9) just after pulling with Avenger's Shield. Next comes Hammer of the Righteous(6), followed by Judgment(9), shield bash(6), Consecration(9), then back to Holy Shield(9). This rotation smooths out your aggro gains and ensures that you are always casting something, never just standing there meleeing.
You can also sub in Avenger's Shield for extra damage/threat when it's cd is up. I usually sub it in for shield bash or HotR, because you'll always, ALWAYS have Holy Shield up, you don't want to lose your mitigation buff from your Judgment (see libram below), and Consecration is good steady aggro buliding (it's also very reassuring to the raid group to see it).
You'll also want to try for Libram of Obstruction when you hit 80. This libram will increase your shield block value by 352 for 10 seconds after a judgment. So basically, using the above rotation, you'll always have this buff during combat. Combine this with Holy Shield, which should also always be up, and this is a great mitigation Libram.
If you'd like more info on gemming/enchants/etc, let me know - but it shouldn't be much of an issue for you until 80.
Happy Tanking! (You'll have to ask someone else about ret, I've been prot since level 10
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