When you target a fellow player or NPC you can
see their current target. For example, this player named Authorized is
targeted, and he is targeting a player named ASAshkir_.
On the top right-hand side of your character portrait you will see an icon with one or two swords. Clicking on this icon will raise or lower your Flag of War. When your Flag of War is raised other players will be able to attack you, and you will be able to attack other players. When it is lowered other players will not be able to attack you. After lowering the flag, you must refrain from PvP combat for five minutes before it takes effect.
Clicking on another player will bring up their character portrait to the right of yours. If you right-click on the other player's portrait a drop down menu will appear that will allow you to interact with them in various ways. The different options include:
Whisper - Sends a whisper to the targeted player.
Trade - Initiates a trade with the targeted player.
Inspect - Looks at the targeted player's gear.
Invite to a party or Invite to a raid - Invites the targeted player to join your party or raid.
Promote to party leader or Promote to raid leader - Promotes the targeted player to the leader of your party or raid.
Remove from the party or Remove from the raid - Removes the targeted player from your party or raid.
Promote to assistant - Promotes the targeted player to be an assistant in your raid.
Promote to master looter - Promotes the targeted player to master looter in your raid.
Move to a new group or Move to an existing group - Moves the targeted player to another group in your raid.
Add to friend list - Adds the player to your friend list.