In PVP your main source of life as priests is your mana bar. If you're running out of mana prior to WoW cataclysm Gold knocking your opponent to near-death, you're most likely most likely to end up to fall over onto the ground. Also, you're at a disadvantage when you face opponents who cut through your Shields or interfere with your spell casting with frequent. It's important to be able to hit your targets while minimizing your damage you sustain. This is among the areas that gear plays a role when it comes to the event of a Priest vs. Priest match the priest who has the more stamina-boosting intelligence will typically beat the others.
The best way to begin with is to make sure Shield Power Word is cast immediately on you prior to the start of a battle and then you can make use of Mind Blast and Shadow Word Pain on your target and then Smite. Smite as they're still close to you. (Obviously it's contingent on being able to jump ahead of the target, but if your opponent can ambush you or get within melee range before you are able to use the spell, then they'll have an advantage against you.) The Shield isn't a necessity in this case, since it's more straightforward to PVP opponents to take on the shield than for mobs. Rogues and mages are likely to rip through it with just a few attacks, while opposing priests and shamans are in a position to eliminate or purge immediately, leaving nothing but the hole in your mana bar. it.
Two spells that are obligatory to use in PVP include Dispel Magic and Psychic Scream. Dispel Magic is extremely useful in that everyone you'll come with will be sporting some kind of buff imposed on them and Dispel Magic lets you remove them without worrying about losing any. Because it's a quick casting, you can repeat Dispel Magic as many times as you'd like until your opponent is no longer able to defend itself with magic defenses at all.
Psychic Scream is a great ability here. In WoW Cataclysm Classic, you might have a difficult time getting stay with them because of their activated racial capability which renders them invulnerable to the effects of fear, however against other races it should be possible to make them run for a short period of time which allows you to kill their enemies, Mana Burn a caster or recover yourself, or run when you're in a difficult situation.
The main issue with PVP is the absence of any effective snare effect. If the enemy is threatening to cheap WoW Cataclysm Classic Gold run and get away, there's nothing you can do except throw spells at their backs and hoping you can take the enemy down before they go far away. There are some ways to slow down or root enemy which mostly involve Shadow abilities (Blackout, Mind Flay) however they're quite cumbersome and insecure.