My personal spec of choice has always been to go a combination of Holy and Discipline. I can still maintain a decent pace soloing and I can still remain viable in instance healing. Believe me, as a non-Shadow Priest leveling, there will never be a shortage of players looking for healers for an instance.
The one I picked for leveling from 70 is a pseudo-hybrid 31/27/3 build.
Power Infusion – Haste every 2 minutes. Keep this up as often as possible.
Surge of Light – Free Smite (or Flash Heal). Watch for the proc and use it according to your situation. Full health? Use it on a Smite. Took some damage? Slap on a Flash Heal.
Spirit Tap – Minimization of downtime. This skill is virtually essential in order to reduce the amount of drinking to do.
Cast your Power Word: Shield up before you open fire. Remember that Holy Fire is a 1.5 second cast when talented. Open up with that spell first, follow up with a combination of Mind Blasts and Smites. Keep doing this until the target you're hitting reaches ~3000 health. Finish it off with a Smite and an Shadow Word: Death. If it still has health remaining, tap your Holy Nova once or twice to make sure it stays down.
Against multiple mobs, keep your Shield up as often as you can. Focus down one mob at a time. If you notice your health getting lose, use instant spells like Prayer of Mending and Renew to keep yourself up. The goal isn't to DPS all the mobs down as fast as possible. It's to go at it slowly and surely while keeping yourself up. You want to try to outlast the mobs as much as you can. If you have Super Mana Potions lying around, don't hesitate to bust one. Your Shadowfiend's a great tool as it can help provide a small burst of damage and provide you with more mana.
Stock up on some Pugnant Seal Whiskey from the local Inn. About 80 is a good number. This is also a good time to use up any stockpiles of Spell damage food that you might continue to have. Super Mana Potions are nice to have in case you need mana in a pinch. Check out WoW Insider's guide to preparing for Wrath with consumables.
Zones of Interest
Check the guide to get to Northrend!
Borean Tundra – Accessible via the Stormwind Harbor for Alliance and the zeppelin from Durotar. It's possible to navigate from Borean Tundra and Howling Fjord without resorting to flying mounts of a continent-wide trek. You get introduced to Malygos. Give Nexus a shot (after you do the various quests in the region to gain access to further Nexus-related quests).
Howling Fjord – Accessible via Menethil Harbor for Alliance and the zeppelin from the Undercity. Utgarde Keep is the first instance you can enter. Don't forget to check out the walkthrough!
Dragonblight – At around 71 or 72, Dragonblight becomes appealing. Most players I've spoken with opted to go to the other introductory zone (Borean Tundra or Howling Fjord depending on which they did first). I suggest diving into Dragonblight as soon as you are almost done the introduction zone. Do the chain quests. Epic cinematic is epic.
Grizzly Hills - Located on the eastern side of Northrend and is a zone above Howling Fjord. You'll run into the Westfall camp here at some point. If you've run Shadowfang Keep before, you'll encounter an old friend.
Getting to Dalaran
Unlike Shattrath City, players can no longer simply ride into a neutral capital. There's a an attunement like quest. There's a variety of NPCs that can port players to Dalaran. You can only get this quest when you're level 74. On the other hand, you can also pay off a Mage or a Warlock to send you to Dalaran. Alternatively, you can get higher level guildies to queue for a Battleground from Dalaran and then AFK out (which should work at any level).
For Alliance – Magister Dath'omere (Valiance Keep, Borean Tundra), Baron von Stromhearth (Valgarde, Howling Fjord) and Magistrix Haelenai (Amberpine Lodge, Grizzly Hills).
For Horde – Image of Archmage Aethas Sunreaver (Agmar's Hammer, Dragonblight). There's undoubtedly similar NPCs in the respective Horde camps in the different zones. I just don't know the name of them since I'm Alliance (cue chorus of boos).
At 71, you learn Inner Fire at level 71. It's the only skill you learn at this level. It's entirely up to you if you decide to boat back to Stormwind or Ironforge to train it. I strongly suggest no if you're bent on hitting 80. I trained my skills at every second level. Besides, Holy Fire is the first DPS spell that gains a new rank (at 72).
For 74, you gain new ranks of Mind Blast, Mind Flay, Smite, and Devouring Plague.
General Leveling Tips
If you want to level as fast as humanly possible, you'll need to streamline your game plan.
- Don't sightsee. I know it's Northrend and it's all new. But if you don't care about the experience and just want to level to 80, you have to go straight from quest giver to objective.
- Do a bunch of quests at a time. Do all the quests at your local quest hub before going back to the hub. You waste less traveling time going back and forth in order to turn in individual quests.
- Forget professions. Leave those to 80. If you're a gatherer, you'll want your Cold Weather Flying training anyway (because it makes it easier). If you're a crafter, hold off some as raw materials are insanely expensive (a stack of Cobalt Ore is going for 300g. Ridiculous!)
Want to find more great tips for carrying out your Priestly duties? Spiritual Guidance
has you covered with all there is to know! And don't forget to check out our other Leveling Guides
as well as our Wrath Guides and Galleries