Knowing the fight
There is no substitute for experience. Someone who has wiped on or beaten a boss encounter is going to have a serious leg up on someone who has never seen it before. You know where to be and when, and you know how to respond to each situation without thinking. Your DPS will be higher, your healing will be in the right place at the right time and your tanking will keep the whole situation under your control. You are totally in the zone for that encounter.
Of course, if you have already gotten through the wiping and are into the defeating cycle of the encounter, then you really don't need any help from me. So how do you get into that zone sooner? How can you reduce the wipes and make the difference in the kill?
The first thing is to do your research. Learn the bosses abilities. This may mean looking through your combat log or some reporting tool (such as World of Logs), but typically it means reading them on a website. Wowhead and WoWWiki are the ones I use most often. Sure, strategy guides will typically give you some details of an ability, but I find it easier (at first) to read them out of the context of the strategy.
A list of abilities on their own won't always make too much sense; what you need is to see how they are applied within the fight. This is where videos are hugely valuable. Try and find one that has been filmed from the point of view of your class or role -- it should make the actual experience feel more familiar. Look for the use of the abilities you read about. See how they are used and look for ways to best defeat them with your character.
The last thing I look at is a strategy. Typically there are a few different approaches to defeat the encounter. You want to be aware of which approach your guild is going to use and look for your role within it. What do you need to look out for? What class-specific abilities are relied upon, and when can you do that neat thing that makes a difference?
Predicting the plays
It's no use being able to recite all the abilities of every boss in Icerown Citadel if as soon as any of them are used, you are taken by surprise and forget what you were supposed to be doing -- or worse, find yourself in a position where you are unable to react. No use remembering to pop Herolust as Saurfang frenzies if you popped it at the start of the fight.
Addons such as DeadlyBossMods are hugely valuable for predicting when an ability is incoming. There's nothing much simpler than a bar counting down the seconds and a trumpet call as it happens. Even if you don't use such an addon, there are typically clues within the fight, if you know what to look for. Maybe the ability only happens at a certain boss health percentage or so many minutes into the fight. There maybe a buff or debuff to look out for. Even without these clues, you will normally be able to watch out for a cast bar or listen for an emote.
Many fights start to throw a load of different things at you to try to get you confused. Once you're confused, decisions start to become less sure and errors creep in. It's a short and speedy road from there to panic. You start doubting your position, messing up your rotation. Your vision tries to narrow and focus on something and misses something else, you don't quite hear what your raid leader is screaming at you and ... well, the result from there is rarely good.
Staying calm under fire is a real skill and something even the most experienced raiders still struggle with. Panic, even in a mild form, is very contagious, so if someone who is losing control yammers or screams over your voice channel, it can be hard not to worry and then head down that road yourself. Try to maintain an inner calm. Tell yourself to relax.
If you have done your preparation and you know what you are looking for and how you should respond, then nothing should take you by surprise. You can look further down the road and avoid the potholes by simply being in the right place ahead of time. Can you be the calm Zen master of your raid group?
Ready Check is here to provide you all the information and discussion you need to take your raiding to the next level. Check us out weekly to learn the strategies, bosses and encounters that make end-game raiding so much fun.