The most important thing on all raids is to follow instructions given by the raid leader and people that the raid leader delegates. Not following instructions on raids is the number one reason for raid failures.
Guides like this can surely help to give people insight about how we raid, but it can not cover all encounters and all situations that can happen on the raid. The raid leader will give important information about the raid at the beginning - especially information related to that particular encounter (what monster the raid is going to kill, what strategy the raid will use, who the Main Assist is going to be, and so on). It is very important to listen well, because the raid leader can not repeat this information more than just a few times. If you think that an important piece of information has not been given, ask in group or in the chat channel; if you do not get an answer, send the raid leader a tell.
The raid leader knows the encounter that the raid is doing very well. The raid leader has a plan for the encounter and the raid leader knows how to win it. The raid leader knows why they set up groups as they did, the raid leader knows why they set Main Assist as they did. Raid leaders spent A LOT of time doing the research of a particular encounter, sometimes several hours. In other words, the raid leader knows what they are doing and why they are doing it. Trust your raid leader.
Sometimes someone may not agree with the course of the action that the raid leader chose. Raid leaders are usually open to any suggestions that anyone has, but unfortunately it's not a very good idea to discuss those in great length on raids, because everyone (and the raid leader especially) is so busy. If anyone has a suggestion or if anyone thinks that the course of action that the raid leader suggests is wrong, please think about whether or not it can wait until after the raid. If not, send a short tell to the raid leader explaining what you think. If the raid leader replies that the original strategy will not change, please follow their instructions even if you do not agree with them.
The raid leader will try to delegate as many tasks as possible to other people, because the raid leader can only do a finite amount of work. The delegated tasks can include the organization of healers, tanks, loot duties, telling the raid about a particular encounter, group setup, or anything else. Each of the people will then be responsible for the delegated area, while the raid as a whole - and its success - will remain the responsibility of the raid leader. When the raid leader delegates these duties, the people who were delegated will be giving orders as well; following those orders is as important as following the orders given by the raid leader.
To make instructions as clear as possible, only the raid leader or the people delegated by raid leader should be giving instructions about the raid. These instructions include the way that a particular encounter will be done, when the raid moves, who the MA is going to be, and so on. In case more than one person is giving instructions, it would be difficult to decode which version should be used. In such an unlikely case, the raid leader's instructions take precedence.
Before, during, and after the raid the raid leader is the busiest person in the whole universe, even during raid downtime (like short breaks, corpse runs, and so on). Please bear that in mind and try to help them by making the raids as flawless as possible.
All raid leader's decisions are final. That does not mean that you should not give any suggestions or that you should not say so when you think something is very wrong. The people who lead most of the raids in DoF are willing to listen and are willing to discuss possible mistakes (and every single person makes them) - but please bear in mind that such a discussion is often not possible during a raid, because it would slow the raid down significantly.