Common courtesy (WoW)  

A very crucial element to playing any on-line game is treating others with respect. The people you play with now will most likely run into you again on another day. Treating others with respect is important in a world where cooperation is often necessary.

There are a good number of different ways to interact with other players. Most of this is common sense, but try to keep each of the following in mind:

Basic Communication

• Players do not like to be spammed or otherwise repeatedly harassed. This can be in private messages like whispers or in the trade channel.
• Within reason, use complete words and sentences. no1 liks 2 try 2 figur wat u mean al teh tim. Typing like that does not make you cool, and it does make you unintelligble (as well as possibly unintelligent.)
• Don't belittle others. There are times when a conversation will get heated, but there's rarely a good reason to call someone a four-letter word, and you can be reported for violating the Terms of Service. People also generally don't appreciate being told to play the way you expect them to -- it is reasonable to expect a priest to heal for a group when they are the only healer available. It is not reasonable to expect them to go back to town and respec Holy.
• Don't spam trade chat with you own troubles. This makes it very difficult for people to sell anything or recieve the services they wish to purchase.
• Avoid randomly inviting people to sign guild charters. Politely ask if they care to join, or if they could do you the favor of signing to get your guild started.

Group Interaction

• Do not randomly invite people to a group without discussing it with them first. Some players may accept, but others greatly resent blind invites. This also goes for inviting people to join your guild. Ask first and you will find you get better results and make more friends.
• Make sure everyone is clear about the goals of the party before beginning. For example, Blackrock Depths is an instance that is split into two separate halves. The first gives you a key to reach the second. A player that finds out after they get there that you already have a key and are only doing the second half may get upset because they wanted something from the first part of the zone.
• Do not join a group you cannot be prepared to finish, or at least be clear about what you can do. Also make sure you show up to a group prepared -- repair your armor before you get there, make sure you have enough ammo, stock up on food for youself (and your pet) unless you have spoken to the mage or another person in the group already who has offered to provide this for you.
• Know your role in the group, and fill it appropriately. Even if you don't like healing, if this is what you and the group agreed, this is what they need from you. If you are a class that can fill a role that you don't want to do, be clear about this from the beginning.
• Let one person lead. Let one person pull. If that person isn't doing their job well, or needs help, offer it, but don't boorishly do your own thing. This is a very good way to get yourself not invited to groups again, even if you weren't the one who screwed up.

Loot

• Loot rules should be in place before any loot drops. If nothing is said, the accepted standard is to roll greed on all greens, and pass on any blues or boss drops you have no direct use for. Enchanters will sometimes roll greed on these items, so roll need if you need those.
• Do not be a Loot Whore. That is, do not attempt to take every single item from the group because you are greedy. It may help you for now, but you will have a hard time getting groups in the future.
• Worse still, do not be a Ninja. A ninja is a player who quickly takes a valuable item and leaves the group before anyone can react, either because it's a very useful item that they face competition for or because it's very valuable to sell. Rest assured, word will get around about you if you are a ninja.
• Raiding guilds will often have their own standards for how loot is done. Know them for your own guild.

While Soloing

• Don't run up and steal a treasure chest or an ore node from someone who was obviously fighting their way to it.
• When you have a common quest goal with someone else, try to work with them rather than against them.
• If you see another person obviously preparing to attack a target i.e. sending their Voidwalker in to the target, don't purposely mount up so that you can beat them to the first blow. Let them take that one, and you go to the next one.
• If you show up to the spawn of an escort quest, and someone else has just taken the NPC and is walking away, don't pull every mob in the area onto the NPC so that the other person fails the quest. Instead, wait the 3 minutes it takes to complete it, and then take your turn.

In PvP

• All bets are off during PvP. While many players have a code of conduct they follow, and try to be respectful of others to engage in fair battles to challenge their skill rather than their opportunism, other players believe in "red = dead." Short of exploits, there's often very little that doesn't go in PvP.
• It is usually considered polite to not begin combat with players many levels lower than you.
• Don't /spit, /laugh or those kind of things after defeating someone.