I just read a thread the other day titled "what is skill" and to be quite honest most of the answers could not have been further from correct. There is a common line you will see from nearly every high end hardcore guild in this game. The most recent trends leaves paragon to be the front runner for favorite high end guild, so right from their wowprogress page "Always recruiting exceptional players."
What does exceptional mean?
Going for a literal explanation straight from the definition "Deviating widely from a norm, as of physical or mental ability, Well above average; extraordinary". So literally they are looking for well above average players for recruitment.
The breakdown
So, what exactly makes up an exceptional player? What does any given player have to do to be seen as exceptional to top players, or even catch their attention? I'm going to give a definitive answer of what I personally look for and have looked for in my five years of high end gaming in the world of warcraft.
What they know, the fundamentals
First off before you even have a shot at being called average you've got to have a fundamental understanding of everything that makes your character preform. What does that mean exactly? It means knowing your talents and abilities, their interactions with eachother, their interactions with glyphs, their interactions with stats, their interactions with set bonuses and trinkets, their interactions with other players buffs and talents, and lastly their interactions with your environment.
What they do, the checklist
High end play is not a rigid priority list firing off in a predictable manner, it's a constant ebb and flow of reaching out to help others and allowing them to help you. Nearly everything happening in a high end raid is on the fly and reactionary, immediate reactions and timing are key which will require keybinding. I'm going to do it a disservice and number things off on a list, this is just for ease of understanding not something to be actually followed in order.
#1. Maintaining your highest output value efficiently and consistently, this is maximum damage healing or threat per second. This is the most basic aspect of playing well, without it you might as well not even be in the raid. Effectively this is the "why you're there" check on the list, it's fundamental.
#2. Maintaining full utility within reason to your situation, this means interrupts, buff uptime and debuff uptime management etc. This is what keeps targets taking maximum damage and dealing their minimum, again fundamentals.
#3. Pre-emptively avoiding incoming damage and negating or reducing unavoidable damage for both you and nearby raid members.
#4. Exploiting fight mechanics to the best of your ability, no this is not the kind of exploitation that gets you banned. This is how you get world firsts, by finding a buff and using every last square inch of it.
#5. Reach outside of your class role and help those around you, misdirects, controllable damage modifiers (tricks of the trade, etc) share them with your raid efficiently to maximize their potential and that of the raid as a unit.
#6. Assuming you're doing all of these things at the same time without slacking at any of them, using ventrilo to communicate if you need help, if the aspect of the fight you control is falling behind or way ahead etc.
Misconceptions
Doing a lot of damage/healing/threat does not make you good, it's what you're supposed to be doing.
Standing in fire does not make you bad in itself, there are no golden rules in this game anything can be optimal or inferior depending on circumstances good play is always about what is best in the moment.
Min/Maxing is not an option, if you're going to take this or any other game seriously you will inevitably find yourself becoming a min/maxer or you will be falling short of your goals.
Reaching your maximum potential as a player is far greater a task than reaching your maximum potential as a character.
The verdict
Can you do more than those 6 points? Always, anyone can always do more and in fact they are encouraged to as opportunities arise during an encounter. As far as golden rules go, I am rather confident I covered the main bases. Doing one or two of these things is just as far from exceptional, as doing all but one of them. You must do all of these things at the same time consistently to step outside the label of average, this game really is about teamwork and tunnelvisioning dps tanking or healing is never going to land you a world first. It's all about communication and knowing your own strengths and weaknesses, asking for help when it is needed, offering your help when it is needed by others, and mastering the mechanics of a fight. The top damage players in the world could fall short of being exceptional if they don't play outside the box and make these things happen. In the end, this is what separates players in top guilds from anyone else.