I've raided for a long time on my priest. My first real raid started with Zul'Gurub before I graduated to Molten Core and Blackwing Lair. Unfortunately, I started late in the game to the point where I never really appreciated AQ 40 or Naxxramas. Years later, I am now working my way towards Illidan after mopping the floor with Archimonde. It's difficult for a holy priest to begin raiding. The learning curve can be steep at times because there are so many options available.
That being said, there are a few lessons I've learned from raiding that have proven universal. They had as much application back then as they do now and I wanted to pass them on to any new budding raid priests.
Check out all thirteen tips, from reagents to situation awareness, right after the break.