Yes, I still owe you an enchant, gem and glyph 101. However, I want to really get all my ducks in a row for it and cover both PvP and PvE glyph choices for all three specs. As one example of how complicated it can get, if you're running exclusively in five man content, you'll use different glyphs for your prot set than if you're raid tanking. I personally switch glyphs several times a day (in fact, my glyph switching has become what respeccing was before dual specs, a necessary step for different tanking situations) - I tend to use Devastate, Cleaving and Heroic Strike as my 5 man majors while I still use Last Stand, Shield Wall and either Vigilance or Taunt for raids. (Sometimes I mix these up and use Heroic Strike or Devastate for my raid glyphs as well.)
Meanwhile, I use arms as my PvP spec and fury as my PvE spec, so in addition to re-speccing every time I intend to do some battlegrounds, I have to put in all new glyphs and even have an entirely different set with different stat weights and gems (for instance, a lot of my armor pen gear has expertise on it that's entirely wasted for my arms spec but needed for my fury spec) -- this all needs to be addressed in any post about gems and glyphing.
But for now, lets deal with a more pressing issue.
Combined with recently announced changes to abilities like Revenge, what we have ongoing right now is a general sense of warriors as a class that requires a great deal more thought than you might expect. Frankly, buffing Devastate basically dropped Revenge off of my keybinds, I only hit it when I am absolutely rage starved and worried about threat. Yes, I'm sure a great many will tell you threat is a non issue in today's game. Those people are wrong. If you're never worried about losing threat, you need to run with better DPS, frankly. Threat is always on my mind, it's half my job as a tank and the big limiting factor for my DPS in most five mans. I can easily rip threat off of even most paladin tanks I run with in my fury spec. Threat is always an issue. You should gear for it as a tank and watch out as a DPS. You have a threat reduction as fury, but no threat dump and no reduction as arms, and as a tank you always have the limitation of rage to make the first five to ten seconds of any pull tricky. One of the reasons I end up chain pulling as much as I do in a heroic is to retain rage and give myself a lead. While DPS and healers often want to stop for mana, stopping to regenerate their resource degenerates mine.
In a raid, one usually can count on more consideration, but it's still not always feasible: Tricks and MD can be on cooldown, waves can spawn, DPS may be tight and have to jump as soon as possible. Tanking the waves of adds on Dreamwalker can be an eye opening experience for just how important threat gearing, gemming and glyphing can actually be. This doesn't mean you should ignore stamina, armor, avoidance stats etc etc, that's not what I'm saying. That would be ridiculous, you'd just tank in DPS gear and hold threat beautifully if that were the case. You'd also die, unless you massively outgear what you're tanking, and you probably can get away with tanking in DPS gear if that's the case. I often tank heroics as fury, I don't even put on a shield or switch stances. If my gear wasn't as good that would be unconscionable and I don't do it with groups I don't know. You do still have threat stats to consider, though. You want strength, you want expertise to at least the soft cap to push dodges off of the table, you want hit at least high enough to allow you to overcome miss chance. (I realize I said 5% in that post, or 163 hit rating. I'd since argue that 8%, 263 rating, is better to aim for.)
Heck, armor value can be a threat stat if you have Armored to the Teeth. Block value is a threat stat, albeit one hampered by recent changes to how Shield Slam is calculated and how block value diminishes. Still, Damage Shield uses block for its calculation, that makes BV a threat stat. Strength is a threat stat for that reason and because it converts to AP, and AP gives us threat from thunder clap and shockwave as well as weapon damage.
The tighter the progression level is the more important a solid balance between threat and survival statistics becomes. On some fights you can afford to go in one direction or another (tanking Lana'thel as soak tank, for instance, I don't even worry about threat stats of any kind, while tanking her as MT I absolutely do but still keep survival in mind as a priority, while on Dreamwalker I pop in threat glyphs and wear several pieces of of DPS gear since catching the adds and holding as many as possible is my priority) but in most cases you need to simultaneously stay alive (corpses are remarkably nonthreatening) and give your DPS as much of a ceiling as you possibly can. I personally want to let that rogue break 15k if he can. If you consider tank threat as a ceiling, consider that each DPSer is limited to staying below this ceiling. The higher it is, the most each DPS player can contribute, and therefore your threat ceiling can be theoretically multiplied by how many DPS players you have to find the rough maximum DPS your raid can do without individual raid members pulling threat and dying. The harder you work, the harder everyone else can work, the faster things die.
There will never be a point where I will feel like I am generating enough threat as a tank. I've been the DPS who had to stop and autoattack because a tank couldn't hold aggro over me, I don't like that feeling. I won't ever be complacent about it and I advise anyone coming into the game as a tank now (whether it be five mans or raids) to understand that the conventional wisdom that threat isn't an issue is overblown. It's plain to anyone who tanked in Burning Crusade that threat certainly is far, far better now. It's not the nightmare it could be then. The power to have good threat generation is in your toolkits and your hands, but you won't get there by ignoring it. A good tank is measured by two standards: how hard or easy is he or she to keep alive, and how much threat does he or she generate?
When I discussed arms I mentioned that one of the things you should do as an arms DPS player is to be active, using your global cooldown, working on a priority list that always kept you active. This is also true for you as a tank. You should be doing things. That's why you have abilities. As a tank you should be constantly surveying the battle, so to speak. Where are the mobs? Where are your fellow players? Is a wave of adds coming, do you have rage, would your time be better spent on single target or AoE? You don't want to spamming cleave or thunder clap on a single target or a boss the way you'd be more likely to use them if you were tanking a wave event like the Tribunal of Ages or Dreamwalker. Is someone off in a corner about to get swarmed? Intervene is made for this situation. Bad warrior tanks are the ones who don't use their abilities in the proper situation. Should you hit shockwave every cooldown? It's probably not necessary, but on an initial pull a thunder clap - shockwave - cleave can do a lot to lock down initial threat and keep mobs focused.
As a tank you should never be satisfied with your threat. Your threat is the ceiling that gives your DPS room to move and grow. While piling on the threat stats past a certain point is counterproductive and useless, you do need to have them. And the more broadly you gather them (not just focusing on hit and expertise for threat, but also using strength and block value and considering armor a threat stat as well) the easier it will be for you. Yes, you should gear for mitigation and avoidance, you should absolutely gear for stamina, but if you do all that and you're under the expertise soft cap which means you can be dodged, and you are low on hit so that taunts are missing and you don't always hit with your attacks, you've become a very easy to heal waste of everyone's time. Get at least 26 expertise. Get as close to 8% hit as you can. Get your strength up, get your armor value up. You can do these things while still getting stamina and dodge and parry, I promise you. Balance your stats for threat, don't just gear to stay alive. Gear to have a reason to stay alive as well.