Whether you get invited through friends, found through the "looking for a group" system, or just randomly are beckoned to follow, there are certain things that you should not do when you join a group.
The most important thing you should not do when you are a follower is to take the equipment and/or gold from a fallen mob. Unless you have agreed upon who will get what, when you are in a group beforehand, you should not take everything from a corpse. Or worse, sacrifice it so one gets anything from it. The leader should set the gold to autoloot (just type 'autoloot' to set this) so that the gold from the corpse will be evenly split between all. Should you notice that the leader does not have this set and you had not agreed upon letting one person get all of the gold, you should bring this to his or her attention. If you still have difficulties, politely tell the leader this is not what you wanted and leave the group. You can do this by typing 'follow
Another popular reason for joining a group is for completing a hard quest. If the quest only allows one person to obtain it, it should be decided from the moment you enter the group as to who is going to get the quest. That is the only person who should be allowed to get this. Going in at the last moment by racing into the next room, saving energy until the final moments to kill the mob, or picking up the item when it is not your quest to do will result in you being kicked out of the group as well as never being asked to come back by anyone else in the group. If the quest allows a group to obtain it, you should wait with the others and accomplish it together. This will show that you are a team player and will probably be asked to team again because you can be trusted.
When you join into a group, it is common courtesy to respect the other people who are in the group with you. You should also listen to the group when the members of the group need to regenerate (commonly said in group talk (gt) as 'regen'). It is to your advantage for the group to remain at or near maximum in health and mana unless there is an absolute need to advance quickly to the next part of the quest or area. There is a reason to do this for every character class. For Warriors, it gives you the chance to regenerate health and movement as well as to notify the spell casters about what protection spells you need. Mages and Clerics need this time to regenerate their mana in order to cast spells for combat as well as healing during battle. Thieves can use the time to change weapons in order to get a successful backstab as well as sneak into the next room. If you do not allow the group to regenerate and continue to proceed, either the group will die from a mob or no one will follow you and you will die from the mob by yourself. There is also a good chance that you will not be invited back into the group.
You should also focus on the group instead of other things. Most of the time you can listen to multiple channels and still actively participate in a group. Some people can even navigate the Internet as they play in a group. If you are in a group and you feel as though channels, in particular gossip and auction, are becoming too spammy and making it hard for you to concentrate you should turn off the channel. To do this, you can retype the name of the channel. After the run, you can turn back on the channel or whenever you feel as though you are better able to concentrate on it. You should also be wary of sending too many tells to people when you are in the middle of a run. It can get you confused and you may miss your team mates asking you for valuable help.
Another way for you not to focus on the group is to leave the group for some time without informing the other members of the group. When you enter into a group, you are counted upon to pull your own weight in a run which includes rescuing party members if you are the tank, healing the others if you are the healer, or just to add the extra force behind the blows to the mobs. If you do not inform someone that you are away, there is a chance you will get another member of the group killed. This is a sure way of having others spread the news not to team with you because you cannot be counted on as reliable.
If you are the leader of the group, you should not leave your team mates behind when you are proceeding into the next room. In order to make sure you do not leave someone on accident and put their character in jeopardy type 'noleave'. That way in case you overlook someone who was resting or sleeping, you will not be able to continue on into the next room. This will reduce the chance of someone in your group dying from being left behind since characters who are sleeping are more vulnerable to attacks.
When you are finished with a group, you should rate the group on how well you think the leader and group was. By typing 'group rate