My personal preference is to spend the first 11 talent points in Holy so as to get Consecration by Level 20. Having Consecration by Level 20 will allow you to complete the Tome of Valor Paladin quest in Westfall (past the Desdmines exit) MUCH more easily than trying to protect Daphne Stilwell from the Defias spawns without Consecration. All you need to do is let the ambush spawn groups of Defias get close to Daphne and then use Consecration to redirect their ire/attention onto yourself, so that Daphne isn’t taking their damage (since if she dies, you fail the quest). Having Consecration also helps you control aggro better in the Deadmines, if your group isn’t intent on running around like chickens with their heads cut off, AVOIDING your Consecration area, after getting overeager and pulling aggro themselves (see: The Aggro Mantra posted above for what they did wrong). 
In the early levels (especially 10-14), Divine Strength feels like the better option over Divine Intellect, but that’s honestly only true for the early game (basically 10-30). Once you start moving into the mid (31-47) and late (48-60) game, Divine Intellect winds up being a better option (because of increased mana pool size, if nothing else), even if you’re wearing Plate armor. At low levels, you’d get +1 DPS out of Divine Strength for every 70 Strength you’ve got on your character, which is a pretty marginal return on investment. Likewise, you need to have “plenty of Strength” as well as “appreciable amounts of Block Value” to reap the rewards from Divine Strength on you Shield Blocking ability, but at low levels (when all of these factors haven’t scaled up yet) the return on investment remains marginal to superficial (see: “twice nothing is still nothing”) in terms of making a difference.
For Levels 15-19, I prefer Spiritual Focus over Improved Seal of Righteousness. That’s because, if I need to heal myself (or anyone else, for that matter) while I’m getting beat on (see: tank role) then I want to reduce the pushback on my healing spells a lot more than I need to be getting an extra +1 Holy damage out of Seal of Righteousness. This is yet another “twice nothing is still nothing” situation. That’s because you need to be dealing 20 Holy damage per hit … base … from Seal of Righteousness in order to add a mere +3 Holy damage per hit from 5/5 Improved Seal of Righteousness. Swinging a 1h Weapon, you’re really not going to be getting that kind of performance out of Seal of Righteousness until around Level 42/50/58. Because of this factor, Improved Seal of Righteousness simply doesn’t DO all that much advantageous for you until you’re heading towards the late/end-game. Starting out as a lowbie, Improved Seal of Righteousness winds up being a LOT of talent points for barely any gain for a 1h Weapon plus Shield user. It takes a long time for your Paladin to mature enough for Improved Seal of Righteousness to be worth it as an investment. In the meantime, until that happens, do yourself another favor and invest in Spiritual Focus. Every time you need to heal yourself while taking damage (which will happen A LOT) you’ll be glad you did. 
At Level 20, invest in Consecration and then try to find a group to help you with protecting Daphne Stilwell at her farm for the Level 20 Paladin quest. I’ve found it extremely easy to convince a Deadmines group to stick together long enough after leaving the dungeon instance to help me complete this quest, even if not everyone stays around to help. All you have to do is keep Daphne alive to the end and you’ll complete the quest. A party of 2 can do this quest, but 3+ makes it almost trivial in terms of success rate.
So starting from Level 21+, start marching down the Protection tree.
Improved Devotion Aura is a “newbie trap” talent. Go full Redoubt instead, even though in this build Shield Specialization is skipped.
3/3 Precision is non-negotiable, and needs to be invested in from Levels 26-28. This cuts down on your Miss chances considerably, increasing not only your DPS throughput onto your targets but also helps prevent Judgements from expiring because you didn’t score another hit to renew duration before their duration expired. Precision makes being a Paladin a lot less frustrating!
Guardian’s Favor is essentially a PvP defensive talent, which is why I don’t invest in it at all, and instead invest fully into Toughness. I would however recommend investing 5 talent points into Toughness at Levels 29-33 so as to maximize the value of your armor protection. Follow up with Levels 34-38 putting 5 talent points into Anticipation to give you overmatch on Defense. For Levels 39-40 put 2 talent points into Improved Righteous Fury (you’re going to start needing it by this point). Level 41 spends 1 talent point in Blessing of Sanctuary.
Blessing of Sanctuary IS MANDATORY and becomes the default Blessing you will use on yourself pretty much at all times. That’s because Blessing of Sanctuary is a Holy damage output multiplier for you, so long as you’ve got a Shield equipped (and you do have a Shield, don’t you?). It’s at this point that you can start using Seal/Judgement of Righteousness full time as a Holy damage multiplier with Blessing of Sanctuary to start really ramping up your Holy damage output, which in turn gets multiplied by Righteous Fury to generate LOTS of Threat when soloing. Alternatively, use of Seal/Judgement of Light and/or Wisdom are available for improved sustain in contexts where it makes more sense.
From Level 42-58 start marching down the Retribution tree.
- Benediction
- Deflection
- Conviction
- Improved Retribution Aura
Benediction mainly makes Blessings, Seals and Judgements cheaper to cast.
Deflection does two things simultaneously, it improves protection/surviability but also improves the opportunities for Parry Haste (subtract up to 40% of weapon speed off the remaining swing timer), enabling more weapon swings per block of time than would otherwise have been possible. This then means not only an incoming damage “cancel” effect, but also a “more attacks/seal procs/judgement procs per minute” bonus side effect … which in turn generates more Threat than the alternative (without Deflection).
Conviction for more critical hits, doesn’t need a lot of explaining. 
Improved Retribution Aura is the “capstone” of investment into the Retribution talent tree because of the fact that Retribution Aura is going to be contributing a SIGNIFICANT fraction of damage potential that can be generated by a Protection Paladin. Furthermore, the threat generated by (Improved) Retribution Aura is also enhanced by (Improved) Righteous Fury, because … Holy damage. So even this choice is about being a better AoE aggro magnet.
For Levels 59-60, circle back to Protection to finish out Improved Righteous Fury (59) and finish out with Blessing of Kings (60), the latter of which can be spammed to generate Threat. Saving Blessing of Kings until the end, when peers have enough attributes to “feel” the +10% to attributes buff just feels more satisfying.
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As for your attributes, when you’re starting out early on, try and pile on as much Strength as you can possibly get, because Strength is increasing both your offense (through Attack Power) and your defense (through increasing the damage reduction offered by your Shield when you Block). Towards the end game, however, if you’re wearing Plate, you’re pretty much going to want every attribute … even Spirit.
Strength continues to offer benefits to your 1h Weapon and to your Shield your entire adventuring career.
Agility increases your armor value (enhanced by Toughness), improves your chance to Dodge, and increases your chances of scoring a melee critical hit, which towards the endgame can actually result in a higher overall melee damage throughput than simply dedicating yourself to increasing your Strength. It becomes the difference between a (for you pleasant, for your target, unfortunate) chaotic spike in damage production versus a reliable steady pressure damage production profile.
Stamina is ALWAYS useful for an aggro magnet, since it offers “margin of error” in the event of unlucky dice rolls against your Paladin.
Intellect is helpful in that it increases the size of your mana pool, and a Protection Paladin will be using a pretty fair chunk of mana on a routine basis.
Spirit is what most people consider their dump stat in their builds, mainly because they would rather /sit in order to eat and drink than spend any part of their attribute budget on Spirit, which often times isn’t doing anything for you during combat, particularly if you’re casting a lot of spells. That’s because health recovery from Spirit stops completely while in combat, and mana recovery from Spirit is halted by the 5 Second Rule of Casting, which you can work around through a combination of cast and channeled spells of long duration to cast/channel, but Paladins don’t have access to that kind of combination of spells to cast. 
Spirit is your “anti-downtime” attribute though, and the more Spirit you have, the less time you need to spend eating and drinking in order to recover your health and mana reserves and resources. This means that with a high enough Spirit attribute (and skillful arrangement of spellcasting timing!), you put less pressure on your inventory for consumables to keep yourself topped up with health and mana. Of course, most Players look at that as an easy tradeoff and would rather spend an inventory slot (or two, or several!) on consumable items than “spend” attribute points on Spirit from their attribute budget. However, as JugsOfLight has conclusively demonstrated, a Paladin who doesn’t need to stop to drink can be quite the force to reckoning with.
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And that’s my take on how to be an aggro magnet as a Protection Paladin. The complicated thing is that in any “benchmarking” solo situation you’re going to be putting a Protection Paladin at a disadvantage relative to their Warrior and Feral Druid peers. I say that because Warriors and Feral Druids don’t have ways to generate Threat for themselves based on what actions other party/raid group members are doing. Only Paladins are uniquely advantaged by being a part of a group in this way. Of course, you can’t exactly run simulations of The Perfect™ Group dynamic to show off a Paladin’s true power as an aggro magnet, because by that point there are so many variables in play that it becomes difficult to attribute success to any ONE contributor, even though the whole group is better off for having brought a Paladin along.
So in that respect, Paladins are uniquely weakened by solo situations, but also uniquely advantaged by groups. Since many of those group advantages don’t show up on the damage/healing meters in a way that can be usefully attributed to the Paladin responsible for those advantages, those benefits tend to be minimized or overlooked in favor of more easily/simply/reliably quantifiable solo performance metrics, rather than the more loosely defined group dynamic metrics.
Needless to say, the build plan I’ve outlined above is the one that I’m pursuing with my Paladin. May the Light shine upon all those who choose to follow in my footsteps.
/pray
/cast Blessing of Sanctuary
/cast Seal of Righteousness