I did it. Climbing the mountain through the snow, both ways... and I had no help from Chuck N. When I started Gowron, I wanted to be protection, not that I had any idea what a tank was, but the lower-damage-receiving-talents looked nice, so I went protection. Now in those days (early TBC) prot damage was low, but these days it isn't that bad. But where to put your talents when you want to level as prot?
First of all, going for a raiding-spec is of course not the way. Most raiding-specs these days have 3 points in Divine Sacrifice/Divine Guardian , but these don't really help for levelling. Most raid-specs although don't have reckoning, it doesn't proc judgements and you need a 2.0-speed (or lower) weapon to take the most out of it, but, for levelling reckoning is a good choice, more swings=faster kill.
And you need to watch out with your mana. At level 30 you can get Blessing of Sanctuary (through talents), at level 40 you can get access to Spritual attunement, and Divine Plea will not be available until level 71. So although DP is golden for tankadins, you won't have acces to it until you are already 3 levels in Northrend. And with that in mind, here comes the talent guide :p
Ok, you reached level 10, probably your first achievement. You know have acces to Seal of the Righteousness, Devotion Aura, Blessing of Might (handy for solo-ing), Judgement of Light, Divine Protection and Lay on Hands. So You already got your 2 oh-shit-buttons, the seal you will be using up until lvl64, your judgement of choice, and the tanking-aura. Not to bad. Your first 5 talent-points should go into Divine Strength. More attack power and block value. Just forget about Divinity, wasted points imho.
At level14 and 16 you get your 2 'taunt'-spells. And at 16 you also get Retribution aura. Now that one is tricky, but what I remember is that it is golden to keep threat on multiple mobs. So you probably will be using that a lot, unless the damage-in gets to high...which is almost no longer the case pre-northrend. You also get Righteous Fury at 16, NEVER TAKE IT OFF AGAIN :p. Second 5 points should go into Anticipation, 5% dodge, your healers will love you (mmm, in my levelling days this was defense-increase).
Bang. You hit level 20 : Exorcism,Consecration and Blessing of Kings. Exorcism is a nice pulling-tool (even if it gets a casting-cost), consecration will stick all mobs to you like glue (so you can probably stop using retri-aura), and KINGS, more strength,armor,crit,intel,spirit and health, yeah, except for the spirit :p. Be happy, your next learnable spell which will be usefull for tanking is at level 64/66 (depends if your allie or horde). So a rundown of talents now.
lvl20-22, Improved Righteous Fury 3/3, less damage.
lvl23-24, Toughness 2/5, more armor, but percentage-based, so not that big an increase at low levels.
lvl25-27, Improved Devotion Aura 3/3, more armor, more healing for the whole party.
lvl28-29, Toughness 4/5.
lvl30, Blessing of Sanctuary
In the next patch, BoSanc will also increase your stamina by 10%, but till then you have to decide if you want to have more health or more mana-return, and less damage. I would choose BoSanc, if only because it's a real sign for : I AM THE TANK.
Now let's look at the things we skipped, Divine Sacrifice/Guardian I already mentioned, just like Divinity (talent of overhealing). Both Stoicism and Guardian's Favor are more oriented towards PvP, just like Improved Hammer of Justice. Although the latter does have more uses in PVE. But these PvP-talents are more suited to retridins doing PvP, then for tanks, who mostly do PVE.
lvl31-33, Reckoning 3/5, more swings, more damage, more threat (see above). 3 points is more then enough here.
lvl34, Toughness 5/5.
lvl35-37, One-handed Weapon Specialization, more damage, more threat, and read it good. It increases ALL damage.
lvl38-39, Sacred Duty, more stamina.
lvl40 Holy Shield
Another bench-mark. You will be using this, always. Never let it fall off while tanking. 30% more block, and it gives a little threat.
lvl41-42, Spiritual Attunement 2/2
Although most raiding specs only have one point here, at this level you don't have access to Divine plea, so max it out.
lvl43-44, Ardent Defender 2/3, this can be a good lifesaver, and will be even better in the next patch.
lvl45-47, Combat Expertise 3/3, more everything :p
lvl48-49, Redoubt 2/3, more Block Value, and a nice proc-based ability.
lvl50, Captain America's Shield
mmm, ok, Avenger's Shield. This will be your pulling tool from now on. it can hit up to 3, but beware of the daze-effect. Although you can play with that. Shield 3 mobs, and then unload the rest of your spells on number 4. No way they gonna pull the first 3 of you.
lvl51-53, Touched by the Light 3/3.
Pre-WotLK, Tankadins needed spellpower, not strenght. But in patch 3.0 all our abilities where changed, so that they also scale with attack power, yup, ALSO. So spellpower is still a nice threat-stat, but tbh, all the spellpower you'll need comes from this talent.
lvl54, Redoubt 3/3
Don't take Guarded by the Light. Although the reduced spell damage is nice, the biggest boon from this talent is useless until you reach level 71.
lvl55-59, Judgement of the Just 2/2, Shield of the Templar 3/3
It doesn't matter in which order you take those, they are both mandatory, reducing your incoming damage by a lot.
lvl60, Hammer of the Righteousness
Another tool to keep threat and do damage on multiple targets. Parties will love you for never loosing threat.
Now it's time to leave the prot-tree for some time, take 5/5 Deflection in the retribution tree, more avoidance is good.
At lvl64 (allie) or level 66 (horde) you'll get Seal of Vengeance/Corruption. From now on, this will be your seal of choice. It does way more damage then SoR.
lvl61-65, Deflection 5/5
lvl66-67, Improved Judgements 2/2, faster judgements, more damage, more threat.
lvl68-70, Heart of the Crusader, more crits for everyone :p
At lvl 71 you'll get Divine Plea. I am not 100% sure, but I think that by putting 1 point in Guarded by the Light should be enough to not get mana-problems. Bw at lvl70 you get Avenging Wrath, if you use your wings before pulling...well..more threat :p
lvl71, Guarded by the Light 1/2
lvl72-73, Pursuit of Justice, faster walking means faster questing, and getting to the bosses faster.
lvl73-75. Conviction 3/5, more crit is nice, not really needed, but you need to put the 3 points somewhere. Alternatively, if you find yourself solo-ing a lot, putting these 3 points into Benediction can also be usefull.
At lvl75 you get Shield of the Righteousness. You know have all tanking abilities you'll need. This is the time to study the 9-6-9 rotation. Basically, you have 6 spells, 3 of them are the 6-second-spells (Hammer of Rightousness,Shield of Rightousness and Avenger's Shield), the other 3 are the 9-second-spells (Judgement,Consecration,Holy Shield). You just alternate between a 6-spell, and a 9-spell. Never using two 6, or two 9-spells after each other.
lvl76-78, Crusade, more damage, more threat.
lvl79, doesn't really matter. you can max out Ardent Defender, or Guarded by the Light, or put one more point in conviction.
lvl80 Respec to end-game-build :p And you get Sacred Shield, which you should keep up, if you have no holy pally healing you (then it is their job)