Monsters
Most monsters in Dungeons are aggressive so you need to be careful about getting unwanted attention. There are also certain monsters which, when aggro'd will cause other monsters to assist. These monsters will also have their aggro transferred to the Adds as well. What i mean by this is if you are a tank and shield smash one of these "key" monsters, it will act as though you shield smashed all of his subordinates as well. This can be handy for keeping aggro, but can also be tragic if you are unable to handle the incoming damage. From my experience, the rock turtles in the alcove next to Kero's room in DMR will aggro in this manner, and a ton of LM monsters will as well. I don't know about CV monsters as i've never been there but i would assume at least some will there as well.
Bosses and Boss Rooms
There are two types of bosses in Dungeons. Mini bosses which spawn every 20-30 minutes, marked as ** mobs, and the big bosses which are marked as ?? which spawn every hour i believe. All of these different bosses have a room that they spawn in for each Dungeon. Usually when grinding in a Dungeon people will "camp" a Boss room in order to kill it upon every respawn. If there is a group already in the room then it is theirs, and any attempt to kill mobs or the boss will almost certainly result in aggressive action from the initial party. Aside from boss mosnters, the room itself has very few mobs and is generally less effective for grinding than in areas of concentrated monsters. With this in mind, some parties will move into side rooms coming off the boss room where monsters spawn more frequently. They will generally grind there and return to the boss room in hopes of killing the boss. In this case, the group does not own the room as they are not currently in the room itself. If another group should come in for the boss then they have every right to take it.
PKing in Dungeons
If you are currently red, meaning you have too many immorality points, you can only be invited into a party if it is a guildmate. Be careful as most people (including myself) will probably try to kill you. Pking in dungeons is in bad taste unless you are assaulted by another group, intentionally mob trained, or are having your kills stolen, most noteably a boss. In any of these cases it is acceptable to retalliate after issuing one or more warnings. If it is just one person i would recommend simply killing them and grinding your immorality off, however, if it is a group and they are kill stealing, there is a better solution which results in no immorality. Should another group steal your mobs have a strider turn on their PK flag and then HeadBreaker the cleric so that he is unable to heal the party. Then procede to Chip whichever character is tanking so they take additional damage from the monster. If this does not outright wipe the other party it will at least force them log out and reform and consider your warning a little more carefully. It may also spark them to turn on their pk flags and have at you. In this case you are free to kill them without gaining immorality. If they should simply continue to steal kills then keep distracting them and hindering their party until they go away. It should also be noted that in 18 levels of dungeon partying i've only had to PK twice, once when someone intentionally mob traind the group and another when my party was assaulted by another group for a boss room. PKing in a dungeon is rare, and this portion of the guide is simply to inform you how to defend yourself in such an occasion.
Dealing with Patrols
Apparently the new update has added patrols to the currently existing dungeons so i'll add some stuff about them. Patrols do exactally that, patrol. Their main purpose is to increase the difficulty of dungeons by creating additional enemies, especially if a party is in a "safe" area. This requires more alertness from the party members and a higher degree of mob and aggro control. As i have not yet DP'd since the update i cannot offer a specific analysis, but in most other MMORPG's an ill-handled Patrol can often wipe a party or, at the very least, require down-time to recoup. As with pulling, having an intimate knowledge of patrols, their spawn times, and their routes is all the better for your success. Now then, down to business. If you see a patrol coming, no matter your class, type "Pat" into the party chat so everyone can get ready for the incoming mobs. The more time you have before they come into range, the more time you can prepair to either move or fight. Pats are to be avoided unless your party is ready for more enemies, unless it's a large patrol, then it should just be avoided. This requires that the Tank move himself and thus, the party, into a safer location away from the incoming patrol. This is where knowing the routes helps as you will know where the patrol will move through and should know where is a safe. In this instance you may be forced to run into other monsters and it is up to the Tank to figure out if it's better to take on the patrol or move and aggro monsters. The inclusion of patrols increases the need for dedicated off-tanks. The rules for pats should be the same as adds (described below), seeing as they are adds. Go figure =/ By the way, again I've not seen Rappelz pats in action, most pats attack in groups so trying to pull one will train the rest. If this is not the case then i'll ammend.