Beginner's Guide to Grouping

Etiquette Tips
When desiring to group with another person. It is considered polite to talk to them before sending a group invite.
Should your group happen upon a chest, supply crate, herb node, mining node ect. Ask before you loot. Most groups do /roll to find out who gets the item.
If you have a spell that will be benefical to the other players in your group, don't hesitate to use it! (AKA Buff your Group!)
When asking for anything from your group, mind your please and thank yous.
Should you need to go AFK, notify the group and add about how long you expect to be gone. Do not be AFK for longer than 5 minutes.
If you have to leave a group before a quest or dungeon is complete, try to find a replacement for yourself. Though not required, it is also polite and considerate to give a reason for your leaving.

Ideal Groups
This section will describe what key elements or classes a group should have if it's expected to succeed. There are always exceptions to this rule because there are many different combinations that will work with the many different classes in the game.
There are 3 essential people that a 5 man party needs for an instance.
Tank - You need someone who can take damage and hold aggro. Warriors, Druids and Paladins work well in this role.
Healer - You need someone who can keep up with healing the entire party. Priests, Druids, Shamans and Paladins can fill this role. If a druid is your main healer, be sure to bring someone else who can ressurect more than once every 20 minutes.
DPS - The rest of your group needs to be filled with damage dealing classes. Any class can fill this role with the proper specs.
10 Man
The larger the groups, the more diverse you can be depending on what classes you have. Be flexible but keep some basic 'must-haves' in mind.
Tank - In a 10 man group you need at least 1 tank, preferably 2. You need someone who can take damage and hold aggro. Warriors, Druids and Paladins work well as tanks.
Healer - Just like a tank, you need at least 2 healers. You need someone who can keep up with healing the entire party. Priests, Druids, Shamans and Paladins can fill this role. If a druid is your main healer, be sure to bring someone else who can ressurect more than once every 20 minutes.
Crowd Control - 10 Man dungeons tend to have larger groups to pull. You need to have some crowd control abilities. The type of CC needed will depend on the dungeon itself but the three most popular CC classes are mages, rogues, and hunters.
DPS - The rest of your group needs to be filled with damage dealing classes. Any class can fill this role with the proper specs.
20 Man
In 20+ Instances you can be flexible but you also have to have certain classes and even sometimes certain talent specializations for boss encounters.
Tank - In 20 man dungeons you need to be more particular about how many of each class you have. Depending on the raid instance, you will need 2-4 tanks which can be warriors, paladins or druids. For raiding you need tanks who are spec'd specifically for tanking.
Healer - Depending on the dungeon you need 2-5 healers. Ideally, all healers will be spec'd for raid healing. Priests, druids, shamans and paladins work well. Try to get a mix of healer classes because of different healing abilities will give you flexibility for boss encounters.
Crowd Control - Most 20 man instances do require 1-3 mages for sheeping. Saps and Hunters traps will work but are not a reliable way to control raid instance mobs who can easily one-shot most members of the raid.
Decursing and Curing - There are bosses in 20 man dungeons that just love to curse and poison and do all manner of debuffs that can wipe a group if they're not taken care of immediately. You need sufficient coverage in your classes to take care of mass decursing. Mages and druids for curses. Priests and paladins for disease and magic. Paladins and druids for poisons. Some bosses you have to designate 1-2 people to just stand there and decurse everyone during the whole fight.
Saviors - You must have someone who can save the group from a wipe. In some dungeons it's hard to get back to where you were unless someone managed to survive to rez others. This can be a hunter or rogue with engineering jumper cables(not very reliable), a Paladin with DI(1 hour cooldown, have a couple backup plans) or a Warlock with Soulstone(30 min cooldown, use wisely).
DPS - The rest of your group needs to be filled with damage dealing classes. Any class can fill this role with the proper specs.
25 Man
This # instance was added with the Burning Crusade Expansion. It is similar to 20 mans but the classes are more dependant on the raid instance itself.
Tank - In 25 man dungeons you need to be more particular about how many of each class you have, depending on the boss encounters. You will need 1-5 tanks, two of which will need to be spec'd for tanking. The others you can usually slide by with an off-spec tank. Warriors, druids and paladins will work well.
Healer - You will need 4-8 healers, depending on the instance. 4 of the healers need to be spec'd for healing. The rest, if not spec'd for healing, need to be partially heal spec or in very good healing gear. Priests, Druids, Paladins and Shamans will work well.
Crowd Control - Many 25 man dungeons do not require crowd control. Those that do require CC are easily covered by 1-2 mages.
Decursing and Curing - There are bosses in 25 man dungeons that just love to curse and poison and do all manner of debuffs that can wipe a group if they're not taken care of immediately. You need sufficient coverage in your classes to take care of mass decursing. Mages and druids for curses. Priests and paladins for disease and magic. Paladins and druids for poisons. Some bosses you have to designate 1-2 people to just stand there and decurse everyone during the whole fight.
Saviors - You must have someone who can save the group from a wipe. In some dungeons it's hard to get back to where you were unless someone managed to survive to rez others. This can be a hunter or rogue with engineering jumper cables(not very reliable), a Paladin with DI(1 hour cooldown, have a couple backup plans) or a Warlock with Soulstone(30 min cooldown, use wisely).
DPS - The rest of your group needs to be filled with damage dealing classes. Any class can fill this role with the proper specs.
40 Man
In 40+ Instances you can be flexible but you also have to have certain classes and even sometimes certain talent specializations. Basically you can take a 20 man group and double it. Or take the rules for a 5 man group and repeat it 8 times. There are also specific requirements for classes depending on what 40 man dungeon you are doing.
Tank - In 40 man dungeons you need at least 4 but preferably 5 or 6 tanks. You need at least 2 tanks who are spec'd for raid tanking, the rest you can get by with off-spec tanks. Warriors, Druids and Paladins will work and in some cases, Shamans and Pet-Tanks (hunters or warlocks using a pet to off-tank a mob).
Healer - You need at least 5 healers for a 40 man dungeon. You need 2-3 dedicated heal-spec healers for the tanks and the rest of the healers can be an off-spec. Priests, Druids, Paladins and Shamans work fine.
Crowd Control - 40 Man dungeons have interesting pulls and depending on the dungeon you may need a rogue for sapping, a mage for sheeping, a hunter for trapping/kiting or a warlock for banishing.
Decursing and Curing - There are bosses in 40 man dungeons that just love to curse and poison and do all manner of debuffs that can wipe a group if they're not taken care of immediately. You need sufficient coverage in your classes to take care of mass decursing. Mages and druids for curses. Priests and paladins for disease and magic. Paladins and druids for poisons. Some bosses you have to designate 1-2 people to just stand there and decurse everyone during the whole fight.
Saviors - You must have someone who can save the group from a wipe. In some dungeons it's hard to get back to where you were unless someone managed to survive to rez others. This can be a hunter or rogue with engineering jumper cables(not very reliable), a Paladin with DI(1 hour cooldown, have a couple backup plans) or a Warlock with Soulstone(30 min cooldown, use wisely).
DPS - The rest of your group needs to be filled with damage dealing classes. Any class can fill this role with the proper specs.

Class Roles
These are the general roles expected of classes as well as what talent trees mean for that class. Classes in the non-raiding environment can fulfill different roles even if they are not fully specialized for it. For example, a Paladin spec'd for DPS can, with good gear, heal well enough for 5 man instances. Or a druid who is spec'd for healing can, with good gear, tank some 5 man instances. It isn't until you get into 60+ content that roles and specs get more concrete for grouping.

Talent Specializations
Feral = Tank or DPS
Balance = DPS
Restoration = Healing
A hybrid class. A Druid can be a healer, dps or a tank. A druid's role in a group might never be set in concrete. If the priest dies, they may have to act as main healer. If the warrior dies, they may have to take over as main tank. In larger groups they could also be asked to fufill any number of roles.
Talent Specializations
Survival = DPS, CC and Survivability
Marksmanship = DPS
Beast Mastery= DPS
As a ranged DPS class you help dish out the damage and kill mobs quickly. The Hunter's biggest challenge in instances is their pet running off and dragging back more mobs than the group can handle. Keep your pet in passive mode and use the commands to tell them to attack specific things only. Keep an eye on the cloth wearers and use your pet to help keep aggro of them. Another useful skill for hunters in instances is their Trapping abilities for Crowd Control. Be sure to make use of it.
Talent Specializations
Frost = DPS
Fire = DPS
Arcane = DPS and Sustainability
You are DPS and crowd control. You help kill the mobs quickly but be careful not to pull aggro. Choose and use your spells wisely. A group generally will like to have water and food too so ask your group before you get started so you're not pausing to conjure in the middle of the dungeon. There are many instances where you will need to sheep a target. Make sure you keep an eye on the sheep so you can re-sheep it if necessary. Use your Frost Nova to help keep mobs away from your healers. You can also use sheep on unexpected adds. Be sure to tell the group which mob you are sheeping so they know not to attack it.

Talent Specializations
Protection = Tank
Retribution = DPS
Holy = Healing
Just a like a druid you are a hybrid class. Be prepared to jump in and takeover any number of roles in the group. You could find yourself healing if the priest dies, tanking if the warrior dies or DPS. Be sure to always use your seals and judgements and auras to help the group. In the middle of a wipe scenario, try to cast Divine Intervention on the priest or another person who can resurrect.

Talent Specializations
Shadow = DPS
Holy = Healing
Discipline = Sustainability
You are a support class. Most groups will expect you to heal. If you expect to DPS instead of heal, make sure the group knows that so they can find a healer. Be mindful of healing aggro, even from vampiric embrace.

Talent Specializations
Assassination = DPS
Combat = DPS
Subtlety = DPS
You are one of the few pure DPS classes. Pay attention to how much damage you're doing so you don't pull aggro. You're not a tank so be careful. Sometimes a group will ask you to sap, make sure you have the right target and be sure the group is ready before you do it.

Talent Specializations
Restoration = Healing
Enhancement = DPS and Tanking
Elemental = DPS
You are a hybrid class. Be prepared to jump in and takeover healing if the healer dies or tanking if the tank dies. Your specialities lie in your totems which will give buffs to the entire group. Learn the preferences for each class that is with you and provide totems accordingly.

Talent Specializations
Affliction = DPS
Demonology = DPS
Destruction = DPS
You are a DPS class. Your DOTS are very useful so make sure you always have them on a target. You can also save a group from a wipe by making sure the priest or another rezzer is always soulstoned. Like the hunter, you pet can undo the whole group if you don't have it in passive mode. Use it's commands to direct specific attacks against mobs. Your pet can also be used to keep mobs off the healers. Occasionally you may need to banish an elemental mob. In these cases, keep an eye on it so you can rebanish if necessary.

Talent Specializations
Protection = Tank
Arms = DPS
Fury = DPS
You are a tank or a DPS but most groups will assume you are a tank unless you inform them you intend to DPS. Use all your abilities to keep aggro off your healer and other weaker party members. Be careful of charging into battle because you may pull more mobs than the group can handle.

Loot Rules
This section shows examples of generally accepted looting rules. Be sure that you ask your group what the looting rules are going to be, just in case they are different from normal. It will avoid hostility and confusion later.
Roll Greed on any BoE Item
Roll Need on any BoE or BoP item that your current character can use, not your alts.
Roll Greed on any BoE crafting items such as gems.
Pass on any BoP Item if your character does not need it (See Rule #2)
If all party members pass on an item, type /roll or /random 100 to determine who gets the item
When coming across a non-mob loot item such as Crates or Herbs/Mines /roll or /random 100 to determine who gets to loot the item in question.

Terms
Add - This means your party has somehow pulled another unexpected mob.
Aggro - This refers to the attention of the mob or who the mob is attacking. If you've gained aggro, the mob is attacking you. If you loose aggro, the mob moved on to someone else.
AOE - A spell or ability that affects an area. For example, a mage can cast Blizzard or Arcane Explosion. A paladin can cast Concecration. A priest can cast Holy Nova. Warlocks can cast Rain of Fire. Generally AoE means to do damage to lots of mobs in a concentrated area.
Bio - Bathroom break. Another way of saying AFK
BoE - Bind on Equip, refering to an item that you may pick up and give or sell to anyone else. If you equip said item, it will become soulbound to you.
Body Pull - To pull a mob to the group by walking up to it. Accidently or intended.
BoP - Bind on Pickup, refering to an item that will become soulbound to you if you pick it up. Can also mean Blessing of Protection, a paladin spell.
Buff - A good spell that boosts an ability
CC - Crowd Control, when a group is looking for a CC, they are looking for a class that can crowd control targets. For example, mages can sheep, hunters can ice trap, rogues can sap, ect.
CS - Counterspell, generally this means someone is asking the mage to cast counterspell on a target.
DE - Disenchant, meaning to destroy an item to get enchanting materials from it. Groups sometimes do this to BoP items that no one can use then the group rolls for the materials the DE created.
Debuff - A bad spell that causes harm, reduces an ability or is just annoying
Decurse - To dispell, remove curse, cure poison, cure disease or otherwise remove unwanted debuffs
DI - Divine Intervention, a paladin ability to save a group from a wipe. This spell kills the paladin and puts the target in an immunity bubble for 3 minutes. Mobs will ignore the person.
DOT - A spell or ability that does Damage Over Time.
DPS - Damage Per Second. Reference to classes who are high damage dealing classes or the amount of damage a weapon does.
HOT - A spell or ability that Heals Over Time.
I'm red - Meaning all the player's equipment is broken and needs to be repaired.
I'm yellow - Meaning all the player's equipment is very close to being broken and needs to be repaired.
Kite - To gain the aggro of a mob and make it follow you, preferably without the mob doing damage to you.
MA* - Main Assist, the person whose job it is to decide what targets die first. All other party members should follow the MA's target so everyone is attacking the same thing.
MC - Usually means Molten Core but sometimes a it means Mind Control, a priest spell.
MT - Main Tank, the person whose job it is to take and hold aggro
Nuke - A powerful spell or combination of spells that do a lot of damage. Usually a term used to describe certain mage spells.
OOM - Out Of Mana, if the healer says this, it's bad.
OT - Off tank, the person whose job it is to take and hold aggro of another target that is not the MT's target.
Pat - Patrol, this is used to reference a mob that patrols around a certain area.
Rez - Resurrect, return a player to life.
RS or Rez Sick - When you resurrect at the Spirit Healer you are afflicted with resurrection sickness a debuff that lowers your stats by 75% for 10 minutes.
Shackle Pull - Priest version of a Sheep pull.
Sheep - A polymorphed target. Before 1.11 a mage's polymorph spell only turned a target into a sheep. After 1.11 mages can also cast other polymorph effects that can turn the target into different animals. The name 'sheep' sticks though. If someone is asking a mage to sheep, they are asking the mage to cast polymorph on the target.
Sheep Pull - Polymorph a target, therefore pulling the rest of the mobs to the group.
Sleep Pull - Druid version of a Sheep pull.
SS - Soulstone, a warlock ability to save a group from a wipe by storing the target's soul so they can resurrect after they die.
Wipe - When a group Wipes, it means the whole group died.
* With the introduction of raid icons in the Burning Crusade, most groups no longer use an MA but rather designate a kill order according to what icons are used on what mobs.

Raid Icons
These are a list of the Raid Icons and what they a usually used for. Exceptions may apply, be sure to ask your group for clarification as needed. A Versatile Icon means the icon can have several uses.
Skull - First Target to kill.
X - Second Target to kill.
Triangle - Versatile Icon. Target is usually Third Target to kill or ice trap.
Diamond - Versatile Icon. Target is Sheep, Sap, Banish, or otherwise CC.
Star - Versatile Icon. Target is usually Shackle or Sheep, Sap, Banish, or otherwise CC.
Circle - Versatile Icon. Target is Sheep, Sap, Banish, or otherwise CC.
Square - Versatile Icon. Target is usually an ice trap.
Moon- Versatile Icon. Target is usually a sheep or sleep.