As you go about life, you learn to communicate in various ways. There is body language, tone of voice, actual words spoken, there are hundreds of different variables. In halo, it isn't that complicated. Because of the simple straight forward signals in Halo, like the "firing" or "under fire" flashes of your teamates icon, the red flash when your shields are down, the red X's above dead teamates, and objective indicators, you only have to worry about what comes out of your mouth.
More often than not, people talk and throw in tons of useless information. This article will hopefully help people cut down on wasted time, effort, and failure to act on information given.
I highly suggest you read my "Team Organization" article before reading this one.
First, let us look at what we which to acheive through communicating to our teammates.
Communication is obvoiusly used to give information to another, but what I'm focused on is what giving and taking that information does.
The first and foremost is to create a fast reaction to various stimuli. If you see a guy at the sniper spawn in lockout, you pass this information on to your teammates so that they will ACT on this information. Telling the the location is a faster way of telling your teammates where the enemy is, much faster than shooting.
The second reason to communicate to teammates is to insure your own survival. When playing in team games like 4v4 Team Slayer, you cannot possibly take on all four; at times, you cannot take on even one. Because of that, you have to rely on your teammates. Telling them important things going on during the game keeps your entire team organized, sharp, and deadly. When your team is acting well, you live longer.
The third reason to communicate is to synchronize. When your team all attacks the same location at the same time, your chances of success are drastically increased. If you play without communicating, you and your team roams around in shambles, and your only kills come from individual skill.
The fourth reason for communication is to, in turn, create a constant flow of conversation. When you talk, your teammates will talk. When your teammates talk, you talk. As soon as you break the barrier of silence, the communication will continue as long as your team is paying attention to the game. As the first three reasons have shown, communication greatly increases your chances of victory over your adversaries.
In summary, you communicate to survive longer, react faster, synchronize your attack, and to keep communication going.
How you communicate is also important. While it would be nice if every team would say "(enemy name) down" and "(weapon) respawned" the moment it happened, saying every little thing is tedious and bogs down your teammates concentration. So you need to forget all the little pointless crap, put your "I freaking OWNED him" stories on hold until the postgame lobby, and focus on what is important. While the list of what is important changes all the time due to all sorts of things, the list I'm about to give you is a fairly general guideline. Use it, understand why I put them in the order I did, and you can figure out when things are important.
Order of importance:
A few of you out there probably have a few quirks with the list above. If so, that's good. Know that the list above generally works, but there are several things that could change the order around. If you are playing a 4v4 CTF, for instance, saving a teamate can be much more important than capturing the enemy flag, noticably when the enemy only needs one more flag to win. Don't take the list above as black and white, and feel free to edit it as you please. Just realize that I made that list with the END of the game in mind. Anything that would help promote one's own personal performance or short-term teamwork was put on the bottom of the list; anything that would help end the game in your favor, at the top.
Now to the actual meat of the article. For those of you who play to win, succeed, and excel, you need to pay very close attention. Go play a few Team Slayer games with 3 random teamates. You will hear something similar to this, if the map you are playing is lockout.
"There's uh.. there's a guy at the place where the BR spawns. THERE'S A GUY AT THE BATTLE RIFLE PLACE GUYS! Not the lift place, the uh, the tower thingy, the place above the needler. By the sword spawn, well, the place you GET to where the sword spawns at, where you fall down, he's up above that to the left. Okay, he's not there anymore. He jumped down. I don't remember where, but I think he has the sniper rifle. Does anyone have the sniper rifle? I don't have the sniper."
Okay, so that's a little over the top. But still, you get the idea. What the above SHOULD sound like:
"One at 3rd floor BR, he has sniper. Jumped down to bottom glass. Going towards sniper tower."
Short, direct, precise, confident. All communication should help you survive, synchronize, and react. After you said the above, you should hear this from your teamates.
"Cutting him off from the elbow"
"Watching from Lift"
"Waiting at Sniper"
Now you all know where everyone is, and you know that the guy coming from glass is a dead man. The player coming from the elbow is going to directly attack the enemy, and has his back covered by the player at lift. The player at lift has a clear view of where the enemy is going, and if the enemy tries to run to the top of sniper tower (his proposed destination), there is another player waiting to ambush him.
When communicating, never yell. Just speak. If you think they may not have heard you, repeat yourself. No sensible person is going to yell at you for saying "3rd floor BR, 3rd floor BR".
Keep in mind that your goal is to help your team synchronize, react, and survive. If the guy has a sniper at 3rd floor BR, once you give his location and weapon, your entire team can lay into him. You aren't just talking to talk, you are talking so that you and your team can ACT on it.
If you communicate well, your team will do better. That isn't opinion, it's fact. It helps your team flow a lot better, and when your team flows better, it helps break up the other team.
After a stint of time with the same players, a lot of the verbal communication vanishes, and is replaced by nonverbal communication. If Ogre 2 sees Ogre 1 with the sniper rifle, he will almost always know how Ogre 1 will play. It would still be important for Ogre 2 to say "one on blue base" or "one at rockets", but Ogre 1 doesn't necessarily have to tell Ogre 2 what targets he is engaging nor where he is going, as he already knows what Ogre 1 will do.
Another point of communication easily forgotten is the status of the power weapons. Most people are smart enough to tell their teammates where the enemy sniper or rocketeer is, but there are dozens of people that don't talk about their OWN weapons.
If you pick up the sniper, the rocket, the shotty, the plasma pistol, the sword, the ANYTHING that your teammates might care to know about, you should tell them. The moment you say "I have rockets", your teammates know that no one else on all of Beaver Creek has rockets, because they won't respawn until they are out of ammo and you drop them. Because of that, the moment you die they know the enemy has rockets (the enemy who killed you, generally). You should also tell them when you are down to your last rocket, or when you are out of rockets, and then tell them when you drop it. Then they can be ready for it to respawn, and the rockets can stay on your team forever. It's a horrible balance issue and a big blunder on Bungie's part, in my opinion, but it's in the game and isn't going away. So use it to your advantage.
Powerups are a biggie too. The Overshield and Camo both respawn on a timer, which means if you say "I got OS" the moment you grab it, your teamates know that it will respawn in X number of seconds. Since you generally have a clock counting down in the bottom right corner, you can be there the moment it respawns.
This article is merely a door opener for those who haven't had the blessing of seeing a professional tournament and hearing pro players communicate. How I wrote above is generally how the pro players communicate. They say only the important information, cutting out the stuttering and foolishness you'd find on X-box Live. mlgpro.com's VoD service should have microphones for the players at the tournaments soon, so you'll be able to hear for yourself how the pro players communicate soon enough. But until then, just work on speaking more efficiently and you'll see an instant improvement in both yours and your teammates gameplay.