K over at More Dots!^2 has a great article on Group Etiquette up. The final section - "Raid Marks/Kill Order and Other Party Irritations" - contains the most universal content of that article. In fact, I'd go so far as to say that it deserved its own article, because it doesn't merely deal with group etiquette. If the things discussed there aren't adhered to, you probably end up with a wipe, it's that simple.
I commented over there on one thing I might have a slight disagreement with, but it's situational, and I don't think it needs a lot of chewing on, being both minor in nature and a matter of opinion.
What I'd like to do is reinforce that content with this to highlight the importance of what K's saying.
It's about control.
Now, there are some that might have a low opinion of us raiding types, but the thing about raiding is that if it were easy, everybody would be doing it. In the same way that PvP is not for everyone, good raiding has its challenges, too, and not everyone is built to deal well with them.
Foremost of these challenges is control. Control of the boss - and occasional adds - being paramount. The MT has to keep control of the boss by aggro management. Healers enable this by keeping the MT alive. And DPS make it pay off by killing the boss without pulling aggro. Pull aggro, and control is lost, and it all comes crashing down.
Control is more important than anything else. If you lose control, DPS doesn't matter, and healing doesn't matter, because the boss is hitting people that aren't prepared to be hit by the boss. If your OT isn't on an add, s/he might get control back, and that is good, but that's like relying on the same parachute for 30 years without a backup. Personally, I prefer not to take that risk. Keep control of the situation and work as a team.
K hits every nail on the head here, and probably says it all a lot better than I. The etiquette portions are icing on the cake, and also well worth the read.