BASIC TEAM INFORMATION
Unlike most other RTS games, CoH is designed so that you are always playing with and against two opposing sides - Axis and Allies. These sides have multiple factions (currently two for each) and each faction can choose one of three specialities (doctrines) to give them specialist abilities and units.
Each faction has been deliberately designed so that they are very different from each other in most respects. CoH does not have mirrored units with different graphics and often units. This means that it takes a bit more effort to become familiar with how each faction works and also means that making the factions balanced overall is more problematic. However it does make the game more interesting.

AMERICANS (Allies): Have less variation in units but their units are often more versatile and in the case of infantry units, larger in size than their Axis counterparts. Americans generally don't have access to heavy armour, unlike the Axis forces.
Americans have a simple tech tree which nevertheless allows some flexibility in choice.
Americans gain veterancy through combat and gain it very quickly. Veterancy for Americans normally gives offensive bonuses.

BRITISH (Allies): Have a bizarre mix of very weak and very strong units and their "teching up" is more complex than the Americans. British are more defensive (apparently) and therefore rely heavily on fixed emplacements rather than mobile support units, which can make them difficult to play. The British faction has a slightly complex tech tree with absolutely no flexibility in research order.
British veterancy is the weakest of all the factions, with only three units being able to gain veterancy, which they then bestow on nearby units.

WEHRMACHT (Axis): Have many more units that are more specialised. This often means they are individually more powerful than their American counterparts but you have to be more careful about which units to use because they are less flexible. They are also smaller in size so suffer more drastically from soldier losses.
The Wehrmacht tech tree has more steps than the American one, but follows the more traditional RTS model, involving researching the next tech level at the HQ. This also allows flexibility.
Wehrmacht veterancy also works differently - it can be earnt through combat but is at such a slow rate that you will almost never see this happen. Instead, veterancy can be bought using the Kampfkraft Centre (KKC) and applies to all units of that type. Wehrmacht veterancy normally gives defensive bonuses.

PANZER ELITE (Axis): Panzer Elite are more like the American faction than the Wehrmacht and are the opposite of the British in that they are mobile, relying on fast, light vehicles much of the time. They have the most generic of all units (Panzer Grenadiers) that can be upgraded with anti-infantry or anti-tank weapons.
The Panzer Elite tech tree is similar to the American model and is very simple as well as flexible.
Veterancy is also similar to the American model, being earned for all units through combat, but is also more flexible in that the Panzer Elite can choose whether to apply offensive or defensive veterancy bonuses (or a mix of both) to each unit.

EXPERIENCE
There are two types of experience within the game, Combat Experience and Command Point Experience. Combat experience is earnt by the individual unit based upon enemy kills and can increase its veterancy, making it more powerful.
Command point experience is earnt by building certain structures and by combat and allows you to unlock the powers specific to your chosen doctrine.
When you see the little green "+3xp" in the game, this is command experience.

DOCTRINES
These are the specialisms you can select within each faction, that gives you access to additional abilities and units. These are more accurately called Companies (American), Regiments (British), Doctrines (Wehrmacht) or Tactics (Panzer Elite), but all do the same thing. Each faction has three of them to choose from.

MAP SECTORS
Each map is divided into a number of sectors. Each sector will be one of the following; a Strategy point (Strat), Fuel point (Fuel) or Munitions point (Ammo). Fuel and munitions are needed as resources. Each sector also gives a bonus to manpower (the third resource) as well as increasing your maximum population size (pop cap). Strategy sectors don't give any direct resource benefit apart from manpower but they link areas of the map together, so controlling one is good and losing one is bad.
One important feature of CoH is that you only get the benefits of a sector if it is linked to your base via other controlled sectors. If the link is broken you gain no resources for it and cannot build structures in it.
Fuel and Ammo sectors are listed as High, Medium or Low. Clever players go for the high ones first and this is where you will see the main firefights. When the map starts, check using the tactical map to see where the highest resource points are.
TIP: Building an Oberservation Post (American, Wehrmacht), deploying a Scout Car (Panzer Elite) or placing a Command Truck (British) on a point gives a bonus to income. In many cases it can also delay the enemy from capturing the point.

COVER
Any unit in cover (especially infantry) receives a big bonus to defence. When you move a unit up against a map feature (like a hedge, ditch, or fence) you will see a series of dots appear - yellow dots mean medium cover and green dots mean heavy cover. If you attack another unit, move into cover nearby so you can open fire with some protection. Buildings also offer cover, as do sandbags. Moving down a road (and capturing a point) gives negative cover (a red shield icon) to show that the unit is more vulnerable.
TIP: Units in cover will start to move around (even if that means leaving cover) when they engage an enemy unit, so you may need to move them back into cover or press "H" (Halt).
TIP: Units in heavy cover actually take more damage from flame weapons.

SIGHT RANGE AND THE FOG OF WAR.
Many units in the game are armed with weapons that can fire further than they can see. This means that if one unit gets within sight range of the enemy, other nearby units outside sight range will also open fire. Some indirect fire weapons or abilities can fire into the fog of war without requiring "sight", but most do and even those that don't, become more accurate with sight.
TIP: Units (especially tanks) often move a lot closer to an enemy unit you have told them to attack than they need to. To stop this, if they are in range but still moving, press "H" (Halt).
TIP: The Computer can see further than you because the fog of war doesn't affect is as much. Therefore computer units can always fire to their weapon range, so they can fire on your units at the edge of their weapon range and often outside your unit's sight range.

INTRODUCTION
Company of Heroes is a very easy game to start playing and on the surface at least, compares with standard RTS games with its structure of buildings that allow units to be created and upgrades for those units.
However the engine underneath it is quite complex and there are a lot of features that aren't immediately obvious (even though their effects will be felt in the game). This guide is designed to explain some of those features and to give a feel for the game itself that may help you when playing it.