Know Your Active Surroundings

Here are some ways to know your active surroundings:

* Look around constantly to see everyone and everything; know what everyone is up to.
* Listen to your surroundings and learn every weapon’s, vehicle’s man cannon’s, grenades’s and grav lift’s unique sound. Also use sound to know when people are near.
* Radar, duh! Check it every half second, you have it for a reason! When you see a dot on it, make sure you can pinpoint its exact location on the map. I know it’s just dots on a circle but if you learn the map well, it can be as valuable as actually seeing what it represents.
* Communicate constantly with your team, shout out position of you, your enemies, what weapons they have, etc. Any knowledge you have, pass on to them from the time you spawn until the time you respawn, through the entire game. Don’t use a mic? You’re at a disadvantage.
* Check the messages at the lower left hand side of the screen. If it says a teammate got “sniped” then yell a warning to your team. Same when it says “lasered.” Know who’s dying and who killed them. The messages show all their names and the special form of death such as “splattered.” EXAMPLE: nOObish Guy assassinated Mr. Lollypop
* Check the score often to know who’s ahead and if you gain the lead, you might want to start camping or switch to Shield tactics instead of Sword Tactics as mentioned in Emerging Impure’s article.
* Halo always keeps markers (waypoints) over your teammates heads showing their UNSC Tag and a colored pointer. The colors give away information about your teammates health.
o Blue means he is fine and not being damaged
o Yellow means he is shooting at an enemy (or shooting the air if he’s just plain dumb)
o Orange means he is being damaged by an enemy
o Red is slightly different. When your teammate dies the entire marker goes red, not just the pointer and the pointer is replaced with a red X
* Every weapon, vehicle, etc., has set respawn depending on the gametype and map. You can count on it having an exact time that it takes to respawn. When counting down the time until a power weapon respawns you could just count in your head and base when to look for it again on experience. I suggest that you use the Forge to check each map for the respawn times of its major weapons and vehicles. This may be knowing passive surroundings but once you know these times you can use it to help you with your active surroundings. Here is a little trick you can use: There is a timer for every matchmade game (lower right hand area of the HUD) and as soon as a weapon is taken or a vehicle destroyed, you can know when it will respawn by using the game timer as a “respawn timer.” EXAMPLE: Timer=6 min. and you just picked up a rocket launcher with a 180 sec (3 min.) respawn time. just subtract 180 sec. (3 min.) from the game timer of 6 min. and you have the exact time the weapon will be respawned. As soon as the timer reaches 3 min., you can go back to get the rocket launcher again.

Knowing Your Passive Surroundings

First of all, you must memorize the maps, their weapons, their vehicles, and everything else about them. Passive surroundings don’t change much (unless you use the Forge) and it is easy to store exact information about them. Here is a list of the major things you need to learn about the maps, most of which is contained in the Maps section.

Reference:
http://halowiki.net/p/Knowing_Your_Surroundings