Discipline Priest
Rotation
Opener: Power Word: Fortitude and Divine Spirit out, Power Word: Shield the tank before the pull, Inner Fire on.
Priority: Shield before damage lands, Renew for ticking damage, Flash Heal for topping, Greater Heal downranked for tank damage. Power Infusion on the top caster.
Cooldowns: Inner Focus for a free Greater Heal, Power Infusion on cooldown, Desperate Prayer as your own panic heal.
Forever notes: Discipline is the mana-efficient support healer; Forever's Nov 2 notes raised healing to match the bigger enemy health pools.
Stats
Healing power (shields scale with it), Intellect (mana pool and crit), Spell Crit (Divine Aegis and Inspiration), then Spirit with Meditation, then mp5.
Shield absorb scales with healing power, so it is still a healer's gear set.
Numbers for every spec and a gear comparer: stat weights.
Where it ranks
See the tier lists for PvE and PvP placement, and Classic vs Forever changes for what Blizzard altered in this class.
Wowhead and Icy Veins keep spec guides of their own: Icy Veins Discipline Priest, Wowhead class guides. Our rotation notes are editorial, written for the Nov 2 tuning.