How to be a successful high end raiding Priest? As a Priest, there is a guide available since World of Warcraft was in closed beta testing stages. Let us have a look at Priest at first.
The Priest class is the master of healing and hate control. Other classes such as the Shaman, Druid, and Paladin can heal, but not as well as the Priest. The Priest can resurrect dead players along with the Shaman and Paladin. But the Warlock has the ability to resurrect, through the use of soul stones. Not only has the Priest some buffs that can help party members and it takes control of humanoid monsters at higher character levels.
It sounds that raiding is simple enough but a Priest has come to raids unprepared for raid event. The priest should know what is expected of the raid to kill a boss. Prior to the event, you'd better to research the strat guides and ask questions. As a whole you know exactly what to expect from the boss.
First and foremost all Priest should bring at least 40 candles on average to insure you have the regents you need to buff your party and if needed to cover another Priests party. Do not ever assume every single Priest in the raid is coming as equipped as you are so prepare for the worst and hope for the best and help insure the raid group as a whole can and will succeed.
Make sure you have a surplus on is Major Mana Potions. Do not assume you will be given Mana pots by guild alchemists when you arrive at the raid. As a Priest it is your responsibility to bring enough items for yourself to provide your healing services from the start to the end of the raid. 5 Mana pots over 4 or 5 hours will not be enough, especially those Priests assigned to major healing rotations. 20 Mana pots per healer for a 4 or 5 hour raid event is suffice and allows you to stand your ground during long endurance fights.
Heavy Runecloth Bandages is one of the most overlooked and last items to make sure you are well stocked. Priests won't be holding aggro which allows you to step back and bandages yourself should you have taken damage during most fights. Mana conservation for those DPS classes that need the healing more than you do for the 10 seconds it takes to place a bandage on yourself. 40 Bandages for a long night of raiding would be prudent.
If the raid will be fighting in Molten Core, insure you bring any available items you have to help increase your ability to resist the primary damage type in the instance.
It is obvious that Molten Core is fire based and as such all healers should have enough gear as back up to provide 120 to 150 fire resistance. This number is the targeted amount a healer would like to acquire during difficult fights. Don't assume a totem or a fire pot will be enough resistance protection during these fights. Come prepared or expect to be rezzed a decent amount.
As with any high end raid boss, not every Priest will spam a flash heal on the tank and DPS classes. If we did all, the Priest would be out of mana and worthless to the raid before the fight was over. To balance this, one to two primary healers are assigned to watch the Main Tank or a rotation of 2 to 4 healers will provide the same service.
Besides healing in a raid setting, a Priest has the ability is that we can dispel magic debuffs off of raid members. By far it is the most reason a wipe can happen during a main boss fight. It is essential that a Priest can utilize this ability to the max especially as a backup healer.