Play a priest? Read this:

http://dwarfpriest.com/

Some highlights:

Rankings of the best healing gear: http://dwarfpriest.com/2008/03/16/the-best-priest-healing-gear-24/

Spell priority for shadow priests: http://dwarfpriest.com/2008/02/21/priest-dps/

Trinkets! Trinkets! Trinkets! http://dwarfpriest.com/2008/03/12/healing-trinkets-then-and-now/

Gems: http://dwarfpriest.com/2007/11/17/gems-for-priests/

Some seriously good theorycrafting here. Check it.