Lower rank spells are getting nerfed come BC.  They will no longer get nearly as much benefit from +damage/healing gear, and will not be mana efficient.  If you are currently using downranking to conserve mana, now is the time to stop and rework your strategy.

I noticed that I am near or at the top of the healing meter on most of the raids that I attend (without excessive out of combat healing.) I will attempt to explain a bit of how I heal.  I am still a noob so you may want to take this with a grain of salt.

My Job as a Healer: 
Keep people alive.  Thats it.   Not necessarily at full health (MT and OT are the exception)

My Second Job:
Resource Management (the part that makes you a good healer).  I can't heal when I'm out of mana or dead.  The 5 second rule and Mana per 5 seconds gear are my best friends.  (I'm still working on the not dead part and any help in this department would be most helpful)

My Philosophy on Downranking:
Waste of time.  The time used casting a lower rank spell is better spent outside of the 5 second rule regenerating mana.  I only use 5 spells when healing.  They are in the order that I use most, max rank: Greater Heal, Renew, Heal, Prayer of Healing, and Flash Heal.  Prayer of Healing and Flash Heal are entirely situational in my opinion.

Healing Priority and what I do about it:
MT - HOT always up - GHeal or Heal as needed
OT - HOT up when taking damage - GHeal as needed
Healers - I know I'm good, but I cant solo heal a raid  :wink: (this is where I usually use flash heal)
Warriors - may have to tank at any time depending on fight (see OT)
Melee DPS - HOT at 92%, spot GHeal as necessary
Warlocks - HOT when at 90% or less - PW:S, FH or GHeal when taking damage
Mage - PW:S before you pull, I usually only heal you guys when you AOE (PW:S, GHeal, Renew, spam FH)
Hunters - PW:S before you pull - You guys are so good at aggro management that I rarely have to heal you  :) 

Potting:
I'm not an Alchemist, so mana potions are expensive. [item]Second Wind[/item] has saved me a butload of gold.  I use this and potions only on bosses and normally no more than 1 per fight.

Overhealing:
I overheal :roll: usually #1-3 in overhealing throughout a raid.  Not an Issue until resource management becomes a problem.

PWN that healing meter:
Get familiar with the tank, and the boss that your fighting.  Time heals to land just after the boss hits the tank, to keep him near full without 5 other people casting a heal at the same time and wasting their mana.  HOT the locks and melee DPS, HOTs are efficient and they know they like it :wink: 

Stuff you probably know:
Skill &gt; Gear &gt; Spec - Heard it, believed it, and put it into practice (respeced to shadow a week and a half ago to learn the ins and outs of shadowform at 60, still healing as well but have a smaller mana pool)

Most of the stuf fhere I have figured out in game, and with the help of a few RL friends that play healers in WOW too  :)