When coming up with a "commandment-style" list of things that every raider should adhere to, I noticed the first two applied to everything else. Really, it all boils down to two very brief principles.
A. Don't be a douchebag
B. Use some common sense
The first of which is actually pretty easy. It's in the bible, even. Now, I don't know the book word for word, but I'm pretty sure the lesson could be paraphrased into "Thou shalt not be a large sack of douche."
The second is a little bit more complicated. What members of the generation before me have considered to be "common sense" doesn't seem to be very common these days. I suppose a less "PC" way of saying it is: Don't be a complete idiot.
Obviously, given that the above statements are at the very core of this post, a monkey with a grease pencil could construct a guide to raiding. Well fuck that monkey. I got here first.
#1: Don't stand in the fire
This applies to fire patches, poisonous or otherwise "ominous" clouds, lightning lines, etc. Don't stand in the dangerous shit.
If it hurts you, the raid, or even just turns on some dude's porch light in China, don't fucking touch it unless your raid leader tells you to.
#2: Never blame the healer
I don't even care if it's their fault. In a guild setting, you have the opportunity to correct any healer issues through other channels, through suggestions from the main healer and other members of the healing ensemble, or through assigned readings from the wealth of articles online.
#3: Bring your goddamn raid mats
Seriously. Get some flasks. Your own goddamn food (spellcasters only are excluded if a fish feast is present). Shut up, sit down and eat. Every minute, of every hour, of every raid. Use them. You know what happens if you do more dps during trash? You get done faster. Which means you get more attempts on the boss. Just do it.
And if I hear one more ret paladin tell me that the fish feast is "just as good" as a piece of strength food, I will explode and take out an entire time zone in the process.
I don't even play your class and I know strength food is better. /backhand
I'm sure I'll get shit for this one. See that shit in the side bar? That's for Fury warriors. And there are about a billion other people, just like me, with websites and blogs dedicated to discussing the mechanics which are specific to your role and class. Go there. Learn from them. And stop doing 3k dps in full 245 gear.
#5: Obey your raid leader
Raid leading is a pretty stressful job. I know, I used to do it on the weekends. Nothing like trying to lead a bunch of casuals (some of which don't like to show up on time/at all) to lower your life expectancy. The last thing they need is some ungrateful little pissant to start spewing their filth about how much we need to do better. If we're wiping, i.e. not killing a boss, then yes, we need to do better. Thanks for the tip, asshole.
Do what your raid leader tells you, and shut the fuck up. I don't care if he tells you to go across your street IRL and slap someone's mom in the face. Either do it or leave, because you are fucking up the program by sitting around and arguing. They're leading the raid for a reason. Respect them or get replaced.
And yes, my raid leader did tell me to slap some kid's mom. I've never felt so satisfied.
#6: Wipe and recover quickly
A wise man once told me that the key to progression raiding was quick wipe recovery. Fast recovery means more attempts on a boss, and more attempts etc. etc. If -one- assbag decides to go check his livejournal between attempts, it effectively slows down the whole thing. It only takes one per attempt to make a night of 15 attempts end up being more like 5.
Stop screwing around and stay at your keyboard. Emergencies happen, but if your bladder is that weak, get a goddamned bucket.
I actually started writing this damned thing months ago, and at the time, I thought I had lots more to pour into it. I am so full of anger and ramen that I thought I could keep it going forever. But a lot of pieces of advice not on the list are somewhat useless. I could talk about loot, and how to behave during distribution, but if you're talking about loot, you already beat the boss, so there really isn't a problem with the raid.
I'll likely add to this over time, or maybe Gincan will come along and drop in his two cents. But I'll have to edit it. I don't think he uses enough four letter words.