WoW Dungeon Etiquette for Noobs

Just a few notes on how to participate, what to expect and what is expected of you.

Empty your bags of excess junk:
Yes. You'll need the room for your swag.

Visit an equipment repairman:
Yes. Just do it and be nicely shined up.

Spellcasters, have a supply of your mana juice:
Yes, it's rude to show up unprepared and have to beg off to an equipment seller.

How to form a group: (Optional)
Presupposing you have a friend or a few friends with whom you would like to enter the dungeon, there are a number of ways to form a basic group. A 'leader' may right click on a name and press the Invite option. Anyplace the person's name appears will do, be it in the Guild (J key) membership list, or the chat display [MYFRIEND], or from the Social panel (O key). Be careful, Invite is right next to the Ignore button, which can be reversed if necessary on the Social panel, Ignored subpanel.

How to queue for a dungeon:
(I key) There is also a button down on the bottom of the viewer that looks similar to a green Eye of Sauron. You will be faced with Role selection, and Random or Specific. If your class may select from multiple roles, you may check box as many as you can, you will be slotted into the first available dungeon you fit. Keep in mind, Tanking and Healer is a more serious role than the DPS, so please, know your role or have patient team mates as you learn.
The Tank's job is to aggravate the enemies into attacking them. The Tank guards everyone. (Maintains aggro)
The Healer's job is to keep everyone alive, if the Tank is doing their role well, this isn't terribly difficult. If the Tank is not, or if an impatient DPS runs about attacking everything, or if the Healer 'over-heals' this is difficult.
The DPS' job is to beat the hell out of whatever the Tank is aggravating. So, let the Tank shoot first before you join the action.
Dungeon Guide flag may be selected as well, but don't do that unless you really do know what you're doing.
Random vs. Specific. Random, will give additional rewards, usually useful, but dump you in a random dungeon. Specific allows you to pick from a menu of dungeons, choose one or more. This is useful for making sure you do every dungeon at least once as you progress, or to follow a narrative with your friends!
The group leader (Or yourself when alone) makes these selections then joins the queue. You will then wait for all the role slots to fill up before being sent off to the start of the dungeon. You do not have to travel to the dungeon, and when you leave the group you will be sent back from whence you came.

Quest Givers:
There are usually a few standing around in the beginning of the dungeon. These are usually worthwhile.

Looting the Good Stuff:
The basic dungeon sets up the loot rules as a sort of Need before Greed. Each fallen foe will round robin the ordinary loot, you'll see sparkles if you can do something with it, but the Good Stuff must be 'Rolled For'. The options are Need (You need this.) Greed (If no one wants it, I'll take it.) Disenchant (I'm an enchanter and can make use of this as materials. (Greed and Disenchant carry the same priority, if an enchanter wins it, it will be automatically reduced to enchanting materials.) and Pass (Don't want it. Bags full. Etc.)

Ordinarily, the Good Stuff will have certain benefits to your class or no benefit at all. The 'tough guys', warriors, paladins, need Str, spellcasters need Int, healers can use Spirit more than a damage dealer but at low levels, if it's a big improvement, just use whatever. Rogues, hunters, use Agi.

Loot Ninja: (Rolls Need on things they don't actually need.)
Examples of loot ninjas:
The paladin who rolls Need on Agi leather armor. (No benefit to the class, really.)
The priest who rolls Need on Mail armor. (Can't even wear it.)
The shaman who rolls Need on a Gun. (Can't even use it.)
How to deal with, call them on it. "Hey bud, uh, that's not for your class."
Usual responses from the Ninja:
Honest Abe: "Oh sorry!" gives it to someone who can use it and doesn't do that again
Greedy Gabe: "I need the gold." (Kick the idiot, you are not their unpaid workforce.)
Silent Sam: Says nothing, either doesn't do it again or keeps needing on everything, often an overseas Gold Farmer. (Kick them if they keep it up, or immediately if you're not so charitable.)

How to Kick:
Right click their frame on the top left, and select the Vote to Kick. You will be prompted with a window to type in a brief reason and confirm. Everyone else will be given a window to Aye or Nay. If the motion passes the player will be removed from the dungeon and a requeue window will pop up to reconfirm your role and another player will shortly join your party to carry on. Your party may carry on short player(s) if you feel up to it. Short a Tank or a Healer, it may be tough going.

How to Leave:
Sometimes... Right click your own panel on the top left and choose Leave Party. You may end up with a Deserter debuff and not be allowed to join a dungeon queue for half an hour.

OMG that guy's HUGE!:
That's a boss. Make sure everyone's ready.

I'm dead :(
Whoops, hang tough, many classes can help you up once combat dies down. If there is none, you may have to Release Spirit and find your way to the dungeon entrance. In many cases, just inside the dungeon entrance there is a Teleportation device to help you along the path to the last major location you've visited.

We're all dead. :(
This is called a Wipe. :) Keep calm, carry on, keep your sense of humour.
Release Spirit as prompted, and follow the Red Arrow on your minimap from the graveyard to the dungeon entrance. It's usually not hard. Some are ridiculous. If you get lost, hang tough, many classes can help you up.

Yay! we beat the last boss!:
Thank everyone. :)
To save yourself from having to walk all the way back through the dungeon to turn in the dungeon quests, (Some dungeons they come to you so hang tough for a few shakes.) On your minimap in the top right there is that little Eye of Sauron. Click on that and select Teleport out of Dungeon. Then do it again and Teleport to Dungeon, you'll be right there in the start where the quest givers were.
If you liked these people and they want to do another, you may requeue with all or some of your party and go again. I think my personal record with a random five was seven times in a row, we had a good thing going. We even wiped a few times trying crazy ridiculous stunts.

Happy dungeoneering. :)