Major glyphs that are most useful as part of a threat glyph set include the Glyph of Blocking, Glyph of Cleaving, Glyph of Devastate, Glyph of Sunder Armor and Glyph of Vigilance. Frankly, the Glyph of Blocking is really only good if your gear is fairly low on block value when using it as a threat glyph, since the changes to block value and Shield Slam. Blocking works as a decent threat glyph when your block value is 1,500 or lower, but above that I wouldn't use it for threat. (It's still useful for mitigation, but in the end, there are probably better choices for you there, too.) Cleaving and Sunder Armor are pure "multi-mob threat" glyphs, and both are fairly solid for that, especially if combined with the Glyph of Devastate so that not only will your Devastate stack two sunders on a target at once, it will also apply sunder to a second target. It does not appear to stack two sunders on two targets, however. As a result, you might prefer Cleaving/Devastate/Vigilance for your threat glyphs.
Glyphed Devastate is a really solid threat generator right now, with Devastate having had its damage output increased recently.
Now, if you end up low on rage for whatever reason while tanking, and only if this is the case, then the Glyph of Revenge and Glyph of Heroic Strike are useful. Frankly, I'm not tanking on a warrior in a situation where I feel like I need the rage, but when I first started tanking and my gear was a lot worse, then this combination of glyphs had absolutely beautiful synergy. Revenge will give you a free HS, and then HS can end up actually giving you rage instead of costing it. But once you're tanking any raid content, these two glyphs will be definitively outperformed by Vigilance/Devastate. Likewise, if your hit is very low (like mine was when TotC/GC was the highest level raid in the game), then the Glyph of Taunt is very useful for fights where taunt-switching is essential. As tanking gear escalates in hit rating (I actually have to work to be below 263 hit rating, for instance), this glyph goes from essential to completely worthless. At 263 hit rating or above, I'd never use it.
The Glyph of Shockwave is very useful if you know you'll be doing a great deal of AoE tanking, possibly alongside Resonating Power and the minor Glyph of Thunder Clap. I personally like either Shockwave/Cleaving/Sunder or Cleaving/Sunder/Devastate for my threat setup, but I don't end up tanking a lot of heroics (and even if I do, I'm not at the gear level those instances were designed for).
For tanking cooldowns (very useful for raid tanking), I find Last Stand and Shield Wall to be very hard to do without if I expect to be taking serious amounts of damage. Tanking heroic Saurfang, for instance, I was very very glad to have a cooldown available every minute. (This is possible since Last Stand glyphed is two minutes, and Shield Wall with Improved Disciplines glyphed is two minutes, so you can use LS and SW once a minute interchangably. Combined with trinkets, you can effectively have Super Last Stand and Super Shield Wall by timing a trinket to use at the same time.)
Minor glyphs that you want to consider as a prot warrior including Thunder Clap (mentioned above), Bloodrage, Charge and Command. I'm personally running Charge, Thunder Clap and Command right now. (Four-piece tier 10 bonus makes the Bloodrage glyph useless, since it not only duplicates the effect but also gives you another tanking cooldown. But if you don't have that yet, Bloodrage is a very useful glyph.) Frankly, with fury warriors in the raid, Battle and Command feel like a little of a waste -- but I'm not really using Mocking Blow enough to want that glyph, either. For someone primarily tanking fives (where you might well be the only warrior), either shout glyph could be a fine choice.
Gems are actually fairly simple. You gem stamina, with dodge, parry and defense gems used only if you need them to reach targets or to hit set bonuses if you particularly like the bonus on a piece. For instance, if you have a piece of armor with a red socket and a blue socket and a 9 stamina bonus for matching, you can pop in a dodge/stamina gem and only lose 6 stamina compared to using two +30 stamina Solid Majestic Zircons. If you are a JC, you will obviously have access to gems with higher stats, but non-JCs will be confined to the universal epic gems.
Likewise, hit and expertise gems will mostly be used only if you're very low on those stats. You want to at least be fairly sure a taunt will always land, and you want to at least push dodges off of the attack table. If you're at 263 hit rating and 26 expertise, you don't need to gem for either and should either gem for pure stamina or avoidance/mitigation stats if you very much want to hit a set bonus. Frankly, if there were an armor/stamina gem (and yes, technically agi/stam does that), I'd recommend gemming that. I personally prefer agi/stam over dodge or parry/stam, but that's very much a personal choice and at this point, I don't really even do that very often, as my set bonuses are usually not worth it.
So I'd recommend looking at your gear. What are you deficient in? Are you able to be critically hit in the heroics or raids you're running? Gem for defense. Are you woefully low on hit or expertise? Gem for those. Otherwise, stamina is probably your safest bet.
For a meta gem, I almost always use the Austere Earthsiege Diamond, as armor is just that attractive as a stat now. If you're hurting on defense, the Eternal Earthsiege Diamond is a possibility. (It's also useful in gimmick unhittable sets, but so far, thankfully, ICC hasn't really had a fight that relied on one of those.)
Enchants aren't just enchants, technically speaking. Leatherworking makes leg armor kits that work as an enchant, and there are shoulder and head enchants sold by various factions. Inscriptionists have access to superior enchants, and if you are a scribe you should be looking at those for your tank. You can only use them on the character with the profession, but they're worth it if you have it. Otherwise, the Sons of Hodir sell the primary tanking shoulder enchant. However, if you feel like you'd rather have stamina over dodge and defense, this level 70 shoulder enchant is still quite good. The Greater Inscription of the Gladiator is a PvP enchant, but 30 stamina is basically a free epic stamina gem at level 80, so if you feel like you would rather have the health than the dodge and defense, it's one to keep in mind.
The standard head enchant, the Arcanum of the Stalwart Protector, actually adds more health than the various PvP enchants, so it's generally superior even without taking the defense on it into account. (Since defense reduces chance to be crit and hit and adds to all forms of avoidance/mitigation, it's almost universally considered superior to resilience for PvE tanking). The Frosthide Leg Armor adds pure stamina and agility (armor and dodge) for a tank's leg slot.
Since most prot warriors take Deep Wounds for threat, Blood Draining is actually a fairly attractive weapon enchant for a tanking warrior. Other options (if you happen to be specced so that your bleed damage is minimal) include Superior Potency and Accuracy. I generally find Blood Draining more useful overall, as it is basically a free smart health potion that can go off more than once during a fight. Even if you spec out of Deep Wounds, Blood Draining is still useful; while it can stack from bleeds, it also stacks from your melee attacks striking an enemy.
For a boot enchant, you can either go with the solid workhorse of pure stamina or get stamina and movement speed, which in today's Aaah ahhagh OMFG the floor is spewing forth death and there's a giant monster about to charge into me which will make him grow 100 times larger and instantly kill half the raid game is pretty attractive. The loss of 7 stamina in return for the ability to move faster when needed is a pretty solid trade for a tank. Meanwhile, for a glove enchant I recommend Armsman, because while attack power or expertise enchants provide static benefits, Armsman scales as your gear and threat improves. For a cape enchant, there's nothing tremendously compelling: you'll go with either 22 agility or Titanweave.
Next week we'll talk about arms warriors.