1. Know your (instance) role
If you've never been in a dungeon before, the idea of group roles may not be intuitive. But when you're working with a group, you'll typically have one person assigned to tank, one person assigned to heal, and the rest of the group dealing damage (DPS). Additionally, some classes have crowd control abilities they'll be called to use in instances -- if you've got one, make sure it's on a hotbar rather than hidden in your spellbook. Whether you're playing with friends or you've jumped into a random group, know what your role is before you go.
Need tips on getting started? Here's some advice on getting started as a tank, getting started as a healer, and tips on improving your DPS.
2. Come prepared
Whatever your role, make sure you come prepared to do it. Make sure you've got the right gear to do your job (and that you've repaired your gear), and that you have food, water, potions, bandages, and any other items you need to play your best. Trust us, it's never any fun to zone into a dungeon with a tank who's forgotten to repair their armor.
We've all played WoW in front of the television, only half paying attention while watching our favorite shows. But when you're in a dungeon, you're working with other people, which means you need to pay close attention to what's going on to your group. And the rest of the group is relying on you to do your job. So if you don't have time to give WoW your full attention, you might consider questing or some other solo activity instead of running a dungeon.
4. If you have any special needs, let the group know
Want to do an optional boss? Only have an hour to play? Just respecced to try healing? Let your group know up-front so they can work with you -- many players will be glad to help out. And if your needs don't align with the group's, it's better to know about it before you've wasted your time running through a dungeon only to skip that optional boss you really wanted to kill.
If you haven't been to the dungeon before, it's worth looking it up to know what to expect. And if you happen to land in a dungeon you're unfamiliar with, let the group know in advance and follow their lead.
6. Stick with the group
Because monsters in dungeons are designed to challenge groups of players, this makes it especially important to stay with your group. If you run ahead or lag behind, you could easily run into a group of monsters you can't handle on your own -- and if your group isn't prepared to take them out, it could mean all of you have to run back from the graveyard.
Similarly, if anyone in the group gives instructions -- like "Don't stand in the fire" -- it's a good idea to follow them. (In fact, it's a good idea never to stand in fire, lava, acid, or anything else that looks potentially unpleasant.) A good group is all about working as a team, and following directions is a big help.
Just like you learned in kindergarden, playing with others means sharing. That means the loot gets split between everyone, and trying to get more than a fair share isn't going to make you any friends. Loot is usually distributed on a dice roll for "need" if you need it or "greed" if you just want it. If you're not sure how loot is going to be dealt with, ask before you get started.
Also, if there are multiple skinners, miners, or herbalists you may take turns grabbing gathering nodes. Let the group know that you have a gathering profession and ask before you take anything! For enchanters, your skills may be called on to disnenchant unwanted BoP items, typically with the spoils split amongst the group later.
8. Be polite
There's no overstating how helpful it can be just to be polite to others in your group. Common courtesy can go a long way towards a fun grouping experience. If you're having trouble, ask for help (and remember to say thank you). And if someone offers you tips, try to take it graciously instead of getting offended (even if they aren't being as polite as they could be). Chances are the other player is just trying to help out!
Unless you're grouping with friends all the time, dungeons can be a real hotbed for drama. We recommend being polite and trying to work with your group as a first (and best!) line of defense against unhappy groups, but sometimes that won't suffice. If you're stuck with a group you don't get along with, remember that you only have to get along with them for the duration of the dungeon run, and then you can go your separate ways. If you want to finish the dungeon, it's best to hang in there and ignore any troublemakers.
But if the group is really causing you grief and keeping you from having fun, there's no shame in calling it quits -- just be polite and let them know you're leaving before you make a break for it. And even if you find yourself kicked from a group, don't be discouraged. Your next group may contain players you'll get along with better.
And now, happy grouping!