Looking back on my raiding career I'd like to think I've changed my playstyle quite alot from my first steps into Molten Core and Zul'Gurub. Maybe my way of progressing from a player who didn't have a clue to someone who does (hopefully) is somewhat analogous to how most players do it? I tried to identify my different stages of raiding and personally I think they correspond pretty well to how people around me play raids too.
Stage 1. I don't have a clue, but hope it works
When I started raiding I didn't know anything about my class or what raiding really was about. I knew it was like instancing, only with 8 times more people. I had done stuff like Stratholme and Scholomance, which were hellishly difficult back then, so I had definitely tried "harder content" and knew what it could demand of me. But still, I wasn't part of a raiding guild and I played shadow. When I got to join a raid it was only because the raiders were desperate for a healer, and a shadow healer worked well enough back then (and you say raids used to be more difficult!). My memories of my few raids through ZG and MC are vague when it comes to my healing. I remember details like cool loot I got (epics, wow...) and that there were people everywhere. I didn't have a clue about tactics, but ran with the group and hoped that would be good enough. Apparently it was, since I don't remember any drama about my noobness. I didn't try to change my way of healing however, I didn't ever think that me dealing with a situation better might actually make much of a difference, and even if it would I had no idea where to start.
I'd like to think of this as the first stage of the raider. Someone who doesn't actually intend to fill his playtime with raids, someone who might not be entirely sure what a raid really demands and means. Someone who is asked to join by friends who know they'll do well enough even with someone around who doesn't have a clue, and who mainly runs around just enjoying everything new. I've been that friend plenty of times. Especially toward the end of Wrath I used to ask people whom I knew didn't usually raid if they wanted to tag along just for fun. The content was easy back then even with one or two people who didn't know all the tactics or everything about their class so instead it was a great way to get to show them something else in WoW, something most of them had only briefly tried in VoA (if anything).
Some players get the taste for raiding from these kind of experiences, but many people who are in this stage of raiding usually are there not because they're bad players who don't get invited to raids, but because they don't have the the time to dedicate to raiding. Since most people either want a regular raiding group or achievements to invite you, getting into a raid only occasionally is tricky unless you happen to know someone in the group already and the content isn't too difficult. Some players stay in this stage out of necessity, but some players move on to the next one. I was one of those players.
Stage 2. Learn to handle the fight
In BC I got invited to more raiding. Love had just joined a guild which mainly consisted of a bunch of irl friends who threw together some raid every week, and they were a healer short. So I got in and decided that I liked 10 man raiding alot more than I had 40 man raiding. Instead of feeling like the 40th wheel, and not have any connection to my fellow raiders at all, I now got into a tight-knit group of friends who were having a blast clearing through Karazhan. This is the first time I really decided to get good at what I was doing, that that in itself would be part of the fun of the game. It wasn't a conscious decision, like me sitting down saying to myself "ok, time to stop being noob!" with the Rocky-montage theme song in the background. But being part of a core raiding group demanded that I actually shape up and started caring about my performance, because other people depended on me.
My first step, back then, was not to start reading blogs and forums about priest healing. Instead I started to learn how to handle each fight separately. Trial and error. This fight needed more aoe healing, this fight needed alot of dispelling, that fight needed me to focus on moving from fire and so on. Karazhan actually proved to be the perfect training ground for an up and coming priest like me, because the difficulty level and the design of the huge amount of boss fights gave alot of practice for handling various situations. Looking back at it, I can't think of a better way for me to get started. Remember that I was still a noob in most aspects, and by "noob" I really mean "newbie". I wasn't a veteran computer game player who knew everything about communities and sharing knowledge. I didn't know that I could use the knowledge of others to improve my own ways, I didn't even know there were people out there who spent loads of time analysing stats into small decimals just to get the most out of their class. I thought that the only way to go about learning was to do it myself. Also I had no priest in my vicinity to ask, I was at the time the only priest in the guild.
Trial and error and learning fights by heart is a great way to get started, but it has a big flaw. If I don't bring something from each encounter, some knowledge about how my class works in general, I will have to start basically from scratch with each new encounter. This was also the case in my case. I remember all the times I thought, after a wipe - "oooh, I should've used that spell there. Well now I know". Instead of thinking about it during the fight. This type of raiding works, and therefore I see alot of people getting "stuck" on this stage. They learn how to deal with specific fights, but they don't carry much of their knowledge on to new fights (kinda like me and maths). You can spot these players immediately. I've played with plenty of people who've been more than decent at doing their job in ICC. But when taking them into a new environment, like when Ruby Sanctum was released or when we decided we wanted to do Ulduar Hardmodes you immediately notice that these people are actually lacking alot when it comes to skill. They take ages to learn a fight and they constantly fail on simple things, until they've tried it often enough. Even if that fight mechanic is just as some other fight mechanic they have done a trillion times! They do choreography great, but they get completely confused when you ask them to improvise or react to something they haven't trained into their backbone yet.
Stage 3. How can I improve?
I was that player for quite some time. It might've stuck with me throughout Karazhan, but somewhere around when we started doing Zul'Aman did I feel like experimenting a little and learn more about my class and healing in general, instead of just in specific fights. I started checking which heals were the most effective overall, which talents that worked the best for various situations and most importantly - why. Why is this heal better than that heal? Why is this stat better for me than that stat? By learning this could I handle with new and unexpected situations better and better and I started to see it as a challenge to deal with a situation not only ok, but as good as I possibly could. Just making sure that we downed the boss wasn't enough, I wanted to make sure I improved something in my own performance with each try. Could I become more mana efficient? Was there something I could've done to prevent that death? I found skills in my skill book I rarely used and tried to fit them into my healing bars. I found a new joy in being able to quickly assess the situation and without really having to think about it, choose the right course of action. In all honesty this is not something I do perfectly even today, and is a big part of what I enjoy about playing WoW still. In each fight is there something which could've been done better, and even if it wasn't necessary in the sense that the fight was a success in any case, it is where I find my challenge today.
As I said I feel like this is where raiders start to differ in play styles. I know plenty of people who, instead of going "what could I have done better?" think "aw, shit happens, nothing I could've done about it". Eventhough that often is the case, some people seem to think that is always the case. It's not just about avoiding failure, it is about the desire to improve. To see improvement as a goal in itself. The goal isn't to succeed with the encounter (exclusively, that is always the goal of course) or to get epics, but to become better at what you do. Unfortunately I feel that is actually rather uncommon among most raiders.
Stage 4. How can you improve me?
Somewhere around the beginning of Wrath did I find out about the vast knowledgebase that is internet. I had only used it to thottbot about items and quests before, but now I realized players used it for debating and discussing too. I started asking other people about advice, I started looking at other peoples thoughts in various matters to add to my own. Discussing a problem with someone else is ultimately the best way to really understand something. Not only do you get the input of another person, but by trying to explain your own thoughts and take on a matter do you better understand what you really mean and think about it. It was during discussions with other priests I got to really think through what priest healing meant and how to go about doing it. Not even Einstein was saved from mental blocks. Just knowing alot about what you do won't save you from simple pitfalls like assuming that you're already doing the right thing without questioning it. Until someone, who might not know as much, curiously asks why I do it the way I do it, and while explaining I realize there might be an even better way to do it.
Nowadays everyone, even new players it seems, know about EJ and various theorycrafters around the internet. If people ask questions about their class in trade or general the general answer is "google it". Reading forums and theorycrafter blogs about your class is something everyone does, but there is still a difference in the way they do it. Like mentioned there will still be the ones that just accept the guides as they are and the ones that will look at them and think "ok, this might be true. But why is it true?". Why is agi better than strength? Why is haste a bad stat? It's not until you feel a desire to learn about these things that you can really learn about how to play your class.
Of course, as we have noticed, most players will do just fine sticking around at stage 2. You can get really far in WoW just by learning a fight by heart. But let me compare PvE to PvP for a moment here. Eventhough you can be a decent pvper just by learning how players generally react and the general best way to deal with various situations, you won't become a good pvper only through this knowledge. It is when you start to learn why people behave in certain ways, or why certain spells are better to use in certain situations than others, that you can start dealing with new and unknown situations. I feel like this is true in PvE as well. A PvE fight is alot more static than a PvP fight, but there will still be things to adapt to all the time. Just as in PvP are you playing with other people who will behave in unplanned and unknown ways, and you being able to act on that in a good way is crucial for your success (the big difference being that in PvP the enemy too is a player). It will make the difference between wipe and kill.
Stage 5. This was never necessary before
The final stage is when you've really become good enough to react to new situations. Even when you do a fight for the 20th time and you've never had to use spell X before, you should be able to notice when it is needed and use it. I won't say that I am in this stage yet, because I don't feel like I am. One of the things I really have to practice is not to become too "comfortable" in the way I handle a situation. Just as described above there can be times when I fail at handling a situation because I just did it the way I always did it and it didn't work. A great example is when we did Nefarian and we had 2 healers assigned to heal the Onyxia tank, of which one was me. We had already done a couple of wipes so I had already assessed how much healing was needed on my target. Suddenly my target takes alot more damage than he is supposed to, my choice of heals aren't enough. I keep thinking that I shouldn't change because this has always worked before. Not until the tank is really low do I realize that something has to be done. Tank dies, and we wipe. Turns out the other healer had forgot his assignment so I was solo healing my target, but I should've reacted sooner to the change. I shouldn't have thought that it would work because it always had, when clearly it wasn't this time around. Even if I didn't know why then, the conditions had changed and I should've changed with them. It might be true that I might not been able to save the tank anyway, but I should've tried!
Like I said, reaching this stage of raiding is what still keeps me at it. In a way I am glad that I don't do everything perfectly, because that would surely make the game boring. If I did everything right and we still fail, I will only blame my fellow raiders. If we fail and I feel like there was something I could've done better, no matter how small, it's ok because I'm glad I learned something.