Thanks to Etheron for rescuing this from the old site for me.
How to prepare for a raid:
1) Do enough dungeon runs to have at least the equivalent of the Dungeon Set 3 for your class. In other words, your equipment should, on average, be level 70 blue gear or better. This doesn't mean that you must have a complete dungeon set; if it did, none of my toons could raid because I don't have that kind of luck with drops. Mine have a mix of dungeon set pieces, crafted blues, quest blues, and raid, PVP, and crafted epics. If you just turned 70, and you're wearing a bunch of mid-60s greens from the auction house, you're probably not ready to raid.
2) Know the instance. If you have to ask where the dungeon is or how many people can go, you are *not* prepared. If you want to go on a raid, you should begin by reading the wowwiki article on that instance. Read about all of the boss fights so that you have some idea of what to expect. If you don't do this, the raid leader will have to waste an extra 20 minutes explaining each fight for you when most of the raid has already read the description and/or done the fight many times. This is one of the things keeping our guild from clearing more of Kara in a night -- out of the three hours we schedule on a given night, an hour or more is sometimes spent explaining the fights. Ideally, the raid leader should simply explain which strategy is to be used and which players will fulfill which roles.
3a) Know the mechanics of your character's primary function. Given the gear you have available to you: How can you do the most damage against trash mobs? How can you do the most damage against bosses? Do you understand why those are two different questions? What is your optimal threat generation talent rotation for tanking? Are you uncrittable? Uncrushable? How do you heal a high-dps short fight? A lower-dps long fight? What is your best shot/hit/talent/spell rotation for dealing damage? What are your primary stats and why?
3b) Know your character's role in a group. If you leveled up to 70 by solo grinding and questing, you are probably not prepared to raid. Solo play and group play are often *very* different. Talents that are invaluable when soloing are sometimes worthless when you're in a group, and vice-versa. (For instance, my warlock's normal grinding rotation is pet attack, DoT, DoT, DoT, lifetap, drain life, lather, rinse, repeat, but that will allow him to do maybe half his potential dps in a group, at best. He has to learn to play differently as a member of a team.) Which of your spells/skills/totems/auras/whatever will most benefit the group you are in?
4) Be fully repaired. Raids are going to mean deaths. 24 other people should not have to sit around for 10 minutes waiting for you to hearth and return because your gear went red on the first (of probably many) deaths.
5) Be stocked up on consumables. Bring all the ammo you can carry. Bring more mana/health pots than you think you'll need. Bring enough battle elixirs, guardian elixirs, sharpening/weight stones, poisons, mana oils, wizard oils and appropriate buff food for 3 or 4 hours and use them. You should never show up to a raid without class-appropriate consumables. Consumables can make more than 10% difference in performance of each person in the raid. When you consider how many boss fights end tragically at 1%, with a big repair bill, spending a little time and/or gold on supplies is a bargain.
6) Pay attention. When the fights are underway or are about to be, you shouldn't be talking in Vent unless you have critical information to convey. For the most part, Vent is for the raid leader to give instructions, and for raiders to announce important issues. When things go wrong, and they will, you need to be ready to pick up some random task the raid leader calls out. If you're chatting about some TV show you're watching when a tank goes down, and nobody can hear the raid leader trying to tell someone else to pick up that mob, you're likely to cause a wipe. When a raid leader asks for questions or suggestions, don't hesitate to speak up, but once the raid leader has determined the plan and has told the raid to get in place for the pull, don't continue arguing that you have a better idea.
7) Be considerate. A raid is not about you, nor is it about the loot you want to drop. You are a part of a team, and that team depends on you to do your best. We're all going to make mistakes, especially when we're learning new fights. Don't make mistakes because you don't care enough about your teammates to bother trying. Make mistakes as part of a learning process. If a fight goes badly, and the raid leader is trying to figure out what went wrong to adjust for the next attempt, let him or her know if you broke CC or failed to pick up your target or if your target resisted. We're not looking for people to blame; we're looking for ways to improve on our next attempt. Besides that, we're going to be looking over some very detailed combat logs anyway, so we're going to find out later. Your raid leader is probably getting tells from 10 different people at any given time, while trying to rebuff, adjust groups, give instructions in Vent, etc. Please bring up questions or suggestions in your class chat channels or with your class leaders before you contact the raid leader directly.
8) Important Addons 8a) Threat Meter -- GET ONE. PERIOD. I strongly recommend Omen, but others will suffice. If you pull aggro on HKM, Gruul, the Prince, et al, everyone dies. Don't be that person. If you hold back too much on those fights because you think you might be generating too much threat, everyone dies. If you tank, you MUST know how your threat generation is holding up against the dps. If you are dps, you need to know if you are about to die or if you're not close enough to death. If you're a healer, and you don't run any other addons that fulfill this role, a threat meter gives you a good idea of who's about to really, really, need a heal, or alternatively, who was showing off too much and should not be healed under any circumstances lest you die from healing aggro.
8b) Damage Meter -- Don't get one to compete for bragging rights; get one so that you know if you're not doing as well as you should be. I don't care if you are a healer, a dpser, or a tank, a damage meter can be very useful. Tanks can use them to monitor TPS (threat per second). Healers can use them to discover that they're only accounting for 10% of the healing in a 10man raid with 2 healers. DPS can see that another member of their class is doing twice the damage with comparable gear. Knowing these things can tell you when you really need to improve and can suggest people to ask for advice in improving. If you can't or won't get one of these, you should be reading the WWS Stats reports I post after nearly every raid. For that matter, you should read them even if you do run your own meter. The WWS stats tell you not only how much you've done, but how and why.
I don't expect you to know the answers to all of the questions asked above, but I do expect you to care enough to try to find the answers. It wasn't long ago that many of them would not have occurred to me. If you don't have experience in groups, try to get guild groups, or even PuG if you have to. If you don't know the answers to the questions, there are great resources available to you, including this very website. Ask your class mentors. Post questions on the class forums. Read the articles about your class on wowwiki, the official Blizzard forums, Elitist Jerks, wowinsder, etc.
