Here's a very quick guide to get anyone up and running on a Prot Pally alt or offspec if you just want to try it out.
Speed tier is entirely optional - Speed of Light is good if you need the sprint, Long Arm is decent because you'll be judging a ton (and it's very good with Sanctified Wrath), and Pursuit of Justice is always a solid, steady increase.
Fist of Justice is the only useful ability to have while tanking. Cast times + tanking = you're gonna have a bad time
Eternal Flame is now the go-to 99% of the time. Sacred Shield (nerfed) is decent if you need to be eating massive hits without heals.
Unbreakable Spirit. Divine Protection on a 30 second cooldown is silly enough on its own - bubble at 2.5 minutes is amazing for clearing bleeds/debuffs.
The 75 talents are where things begin to get interesting and really depend on how you play the spec. If you have a low iLvl, I highly recommend Holy Avenger, because it assures that you'll have 100% active mitigation up when it's used. I personally use Divine Purpose most of the time, because it gets very good with Haste. Sanctified Wrath is good if you ever need the 20% healing bonus, and it plays well with Long Arm of the Law.
The 90 talents are preference again. Holy Prism hits hard as prot and heals for a good amount - it's especially useful in 5 mans. Light's Hammer deals amazing AoE damage and healing, so use it in add fights. Execution Sentence hits like a freight train, so it's very good on single target bosses.
Use Focused Shield on single target. Glyph of Word of Glory is awesome because the damage boost is very noticeable as Prot (you'll also be using Eternal Flame every so often). Final Wrath is nice on fights where the execute range sucks. Divine Protection is situational - think about the fight ahead of time.
The General Priority
Keep up Eternal Flame. Try to use if at 5 stacks of Bastion of Glory (use WeakAuras or similar to track this, it's important), but refreshing the HoT is more important than having the 5 stacks.
Keep up Shield of the Righteous as much as possible. This is your active mitigation and prevents you from being slapped around.
Use Crusader Strike for Holy Power.
Use Judgement for Holy Power.
If all else is out, start using fillers. The order of this is Avenger's Shield > Level 90 ability > Holy Wrath > Consecration. Consecration moves up slightly in AoE.
Higher iLvl gear always wins regardless of secondary stats - keep that in mind.
Hit (7.5%) = Expertise (15%) > Haste (to 21,000) > Mastery > Parry = Dodge > Excess Haste (You won't reach 21K in Prot gear unless you're very lucky)
For 10 man, gem for as much Haste as humanly possibly. Yellow sockets are Haste, Blue are Stam/Haste (use hit if you need it), and Red are Expertise/Haste.
For 25 man, gem for enough Stam in order to survive the extra damage. If you feel that you need more stam, mix in some solid blue Stam gems, Stam/Haste in yelllow, and Stam/Exp is blue.
Enchanting is the same idea. Get haste and stam whenever you can. Use Dancing Steel or Windsong (they're both good).
yep you are J