You might have seen players walking by and not known how to communicate with them. You might have also seen lines of text whizzing by in the general chat channel for your starting area. In general, any action you want to take that isn't done with the mouse is a "slash-command", meaning it starts with a front-slash.
Type /wave, and press enter, for example. Your character will wave at the open air, and a message will say so. This is called an emote. It is one of but many kinds of slash commands.
So how do you talk to that person next to you? Type /say and before you hit enter, follow it up with a message. (/say hi.) The /say portion will probably disappear after you press space, for reasons that will become clear later.
There should even be a speech bubble that appears near your character, indicating that you are talking. /say is the command for talking to people immediately next to you, but perhaps you want to talk privately to someone. In this case, you can use /tell followed by the person's name, and the chatbar will instantly change to purple, indicating that you will send a private message to that person. Now whatever you type next will simply go to that person. As an alternative to "tell", you can use "whisper", or abbreviate to just a 't' or a 'w'. In other words...
...are all the same thing. They will give azuarc a message of "hi".
What about that brownish text [1. General - Dun Morogh] that keeps floating by? That's simple. Start a message with /1. (/1 Hey everyone, I'm new here.) Anything you type in the /1 channel will go out to everyone that is in it, which will be basically everyone in your starting zone. Don't be a loser and spam everyone with useless crap, but don't be afraid to use it.
However, if somebody else is irritating you and you want to leave that channel, you can type /leave 1 (for channel #1, which should be general). If you leave general and want to come back, type /join general. Channel 2, only in cities, is the Trade channel. Channels 3 and 4 are for announcing when places are being attacked by the other faction; you might very well want to leave this.
If you want to know if a particular person is on-line to send a tell to them, there are two things you can do. You can try to send the message anyway, and get an error message if they don't exist. Or you can check if they are logged in first by using the /who command.
Typing /who allakhazam would do a search to see if there was anyone on with allakhazam as their name. Partials also work, so you could also find Al by typing /who alla.
The who command also works for classes, level ranges, races, guild names, and a bunch of other stuff. There is a chance if you try it on something more general, like /who warrior, it will bring up the social menu.
The social menu is the button with the ! in a balloon that can be brought up with the O key. Under the who tab, you can do the exact same things as with the /who command. Longer lists will automatically go to this window though.
Also in the social menu are the friend and ignore tabs. In these submenus, you can make lists of people that you want to regard as friends or whom you want to block all message from. In general, don't put people on ignore unless they REALLY tick you off, and take them off later. If you want to add someone to your friend's list, it will tell you in this menu if they are on-line, where they are if they're logged in, and you will also get log-on and log-off messages in your chat window for them.
There are three other possible tabs in the social menu which you might not have, guild, chat and raid. If you are in a guild, the guild tab will tell you who is on-line from your guild. Guild members also give log-on messages by default. The raid tab is simply a listing of the people and groups in your raid. (A raid is two or more groups linked together.) The chat tab will show you who is using the global channel you are currently in.
Since we've mentioned all the other menus, we may as well talk about the last two buttons on the menu bar. The computer button is the options menu. It gives you a choice of options relating to video , sound, interface, or macros, plus the choice to log off or exit the program. The question mark button is the help window, if you need to petition a game master. (The window will explain when it is ok and when it is not to look for the help of a GM.)
One last thing about working with other players. If you want to get into a party with someone, target them, right-click their portrait, and pick invite. This will give them a pop-up window asking them if they want to join your group. (Or maybe they will invite you first!)
You can have up to five people in a group, and while grouped, you split experience and potentially the items that drop. Quests that aren't "collect" quests are usually easier in a group, so if someone is doing the same quest, invite them!
In a group, /party or /p will talk to your teammates. Note that once you've used this once, just pushing enter and typing will default to party. (Before, it would have been a 'say'.)
The group leader will have a crown next to his or her portrait. If you are the group leader, and you right-click your own portrait, you can set the loot mode for the group. "Group loot" means that everyone takes turns, but you will get a pop-up to roll for higher quality items. Round Robin is the same without the rolling. Free-for-all is no restrictions. The other options aren't as significant.
If you are in a group and a corpse is yours to loot, it will sparkle yellow. You're probably used to that by now. If it is not your's to loot, though, you will not get sparkles. Money is automatically split in a group, so under group loot.
If you want to leave a group, right-click your portrait and select 'leave party.'