Usually Retribution Aura when tanking trash and Devotion Aura when tanking bosses, learning new instances, or on a difficult pull. For some bosses you'll be better switching to one of the resistance auras.

Pull with Avenger's Shield, that should hit most of the mobs in a trash pull, Consecration when they're closer, maybe Holy Shield as well, then Hammer of the Righteous, sometimes I'll use Judgement of Wisdom, but most of the time it's not needed when I have Mana Spring Totems, a Mana Tide every 3 minutes, Inervate and Glyped Water Shields. My Pally never loses aggro to my casters unless something actively causes him to (like gouge from Rogue-type mobs).