Solo Questing:
To start off, I have Seal of Command on and Blessing of Wisdom as my blessing.
On a single mob, I start with repentance (assuming I can, otherwise I use Hammer of Justice), then quickly follow with Judgement of Wisdom. Replenishment and Crit. Then I use crusader strike, followed by Divine Wrath to replenish my health. By this time the mob should be about two-thirds dead. An auto-attack and a Hammer of Wrath for the kill.
With this you can solo indefinitely. I grinded all of Nagrand at 65, finishing every one of the "Hills of White Elekk" quests without ever having to eat or drink, because of the Art of War FoL proc and the mana replenishments from crits.
PvP:
SoC and BoM
Start with Hammer of Justice (or repentance, I'm still playing around with which stun to open with. For the sake of simplicity I'll just explain HoJ). If it's Hammer of Wrath, I'll consecrate while they're stuck there, use JoL or JoJ (the latter being for a caster/hunter or the like). Crit, replenishment, FoL proc for the next 15 seconds. A quick Crusader Strike and Divine Storm. Then an auto-attack and they're unstunned. If they're intelligent they'll hop off my holy ground, and I can repentance them. I've probably taken some damage now, so I'll use my instant Flash of Light, and as a Draenei, I use my racial heal at this time (If I have it). Another Judgement, Crusader Strike, Divine Storm, Hammer of Wrath and they're done.
As far as instances/raids:
No clue. I haven't done enough as Ret to justify me submitting any advice.
WOOOT! FIRST POST! Haha hope I helped :p