WoW Priest Guide - Leveling a Priest: How To Do It Right

While leveling my Priest to 60, I tried out multiple specs and strategies, and found the best possible way to grind to 60 in regards to both speed of kills, amount of downtime, and exp/h in general. After experimenting a little, I gave my friend a spec to help him level his Troll Priest to 60. After 35 levels, it's going extremely well; he loves it. He had played a Shaman and 2 Mages to 60 and aided leveling a Warlock and Druid to 60, yet still you'll hear from him, "I love Spirit Tap". I tried grinding myself, and it works extremely well. We have zero downtime and are able to easily break 20k/h as low as level 35.

The Gear

You will be Wanding a lot... a lot. It's important to wand to allow your mana to regen. Stock up on Spirit gear. Buy some stuff at the AH for cheap. Get massive Spirit gear! It'll make grinding so easy. Collect all Cloth gear from SFK. Run SM like a bot in your 40s. Don't waste money on Staff of Jordan; you can get Zum'Rah's Hexing Cane (http://www.thottbot.com/index.cgi?i=38853) a few levels later by running ZF a few times and it's a better staff. Always get the highest possible DPS wand for your level.
Look up "cloth armor 20-40" at the AH. There are tons of great Spirit items that'll help you a ton if you're willing to spend a few 10g's.
There isn't much +spirit gear that has +damage on it, and Spirit is your primary stat. Avoid 'Shadoweave' gear in your 40s... the +damage isn't worth the Spirit loss. Darkness and Shadowform offer all the +Damage you need.

Remember, Spirit > Damage > Intellect = Stamina, just don't gimp your life too much, especially on a PvP server.

The Talents

10-14: 5/5 Spirit Tap
15-19: 5/5 Wand Spec (I'm serious.)
20-21: 2/2 Imp SW:P
22-24: 3/5 Shadow Focus
25: Mind Flay (This skill SUCKS before lvl36 anyway)
26-27: 5/5 Shadow Focus (HIGHLY recommended over Blackout)
28-29: 2/2 Imp Psychic Scream (Filler)
30-31: 2/2 Shadow Reach
32-34: 3/5 Shadow Weaving (Best available, not a grinding talent)
35-37: 3/3 Focused Mind
38: VE
39: Silence
40: Respec to
http://www.worldofwarcraft.com/info/classes/priest/talents.html?000000000000000000000000000000000000000000500252010051103051000
41-45: 5/5 Wand Spec
46-47: 5/5 Shadow Weaving
48-49: Whatever you find yourself needing. If you chose to use VE and want more healing, Improve it. If you use Mind Blast a lot, get Shadow Power. That's probably what I would do, it'll help more as you progress in levels.
50: At this point, I would do another respec. Yeah, respecs may cost a bit of money, but it's what helps grinding, and you'll make the 6g back in Outlands in about 2 minutes.
http://www.worldofwarcraft.com/info/classes/priest/talents.html?000000000000000000000000000000000000000000500252010251103051251
51-55: Unbreakable Will or Wand Spec, depending on what you want. They both kind of suck equally at the period you're at. I guess Wand Spec would be better overall for grinding.
56-57: 2/2 Martyrdom, this and Imp PW:S will be nice for Mind Flays.
58-60: 3/3 Imp PW:S
61-63: 3/3 Meditation! Congratulations on 60, you now have a third excellent mana talent to further aid you. Try and fit this talent into any build you make, except I suppose Arena Shadow.
64: Inner Focus
65-67: 5/5 Shadow Power
68-70: Whatever you find yourself needing.