Below are several tips to help new players.
Grab Town Centers As Fast As Possible
In all games, with the exception of some campaign levels, town centers are key to producing more units. Train fast units to explore and take over town centers before the enemy takes them. Scouts cannot take over town centers. Train defensive units to protect your newly conquered towns from enemy exploration units.
Start Building immediately
Buildings are very important. If an attack is expected, build walls or defensive towers. If enemies are not nearby, build troop generation buildings such as barracks to help generate an army.
Build A Mixed Army
Creating an army out of a single unit type will result in that army being eliminated by an enemy mixed army. Use a combination of defensive/melee units, ranged units, and healing units to fight against enemy armies. Train a mix of spearmen and swordsmen, as they have different strengths and weaknesses
Pick Battles Wisely
Units are weak to some and strong against others. Attack enemy units with units that are strong against them.
Archers [Archer]: Weak to cavalry, skirmishers and heavy infantry; Strong against swordsmen and flying
Skirmishers [Skirmisher]: Weak to only cavalry particularly, but low hp; Strong against archers
Heavy Crossbowmen [Pavaise Crossbowman]: Weak to cavalry, heavy infantry, and skirmishers; Strong against swordsmen, flying, heavy infantry, and heavy cavalry
Heavy Cavalry [Knight]: Weak to pikemen, heavy crossbowmen; Strong against swordsmen, archers, skirmishers, and heavy infantry
Light Cavalry [Light Cavalry]: Weak to pikemen; Strong against swordsmen, archers, skirmishers, and heavy infantry
- Light cavalry receive less damage from pikemen but are weaker in terms of attack, hp and armour relative to heavy cavalry. Their bonuses and speed are often greater though.
Pikemen [Spearman]: Weak to none notable specifically (foot power range units), but low hp; Strong against cavalry
- Note that bonuses increase with the weight class of cavalry. Pikemen can get first strike after research, which increases effectiveness relative to all melee units. Foot power range units deal only slightly greater damage against each individual pikeman but drastically increase in effectiveness when there are more polearm wielders. Only Winged Hussars and gunpowder units (among melee cavalry) can stand against pikemen after first strike research.
Swordsmen [Swordsman]: Weak to archers and cavalry; Strong against structures, siege machines, and ships
Shielders [Shielder]: Weak to cavalry; Strong against structures, siege machines, and ships
- Light Shielders are also effective towards ranged units. Typical (heavy) shielders have full counterattack.
Heavy Infantry [Foot Knight]: Weak to cavalry; Strong against structures, siege machines, ships, swordsmen, and archers
- Units that ignore armour, blunt weapon wielders, and poisoners are also effective counters to heavy infantry.
Siege Machines [Catapult]: Weak to melee units, fire; Strong against structures and ships
- Gunpowder units are generally more effective than normal siege machines.
Attack Ships [Galley]: Weak to anti-ship ships, siege machines, swordsmen, fire; Strong against transport ships
AntI-Ship Ships [Trireme]: Weak to siege machines, swordsmen, fire; Strong against ships, siege machines, and structures
Flying [Ornithopter]: Weak to ranged units (especially archers), fire; Strong against melee units
Hybrids of similar cost are less useful in filling any one role and have the weaknesses of all their parent classes. Avoid engaging stronger enemy units with weaker units in melee (ranged attacks have no risk of retaliation in most cases). If you have to (as in some campaign maps), try attacking first and minimising damage received. Healers are adept at converting units with low mental resistance (e.g. Elephant). Workers can stall enemy units not suited to dealing with structures using light fortifications (e.g. Frisian Horse).
Defend Your Support Units, While Attacking Your Enemy's
Builders, Healers, and Archers are generally low heath. Eliminating enemy builders prevent your opponent from building structures that can swing the battle. Eliminating enemy healers prevents your enemy's army from recovering health.
Utilize Choke Points
A narrow area, such as a bridge, or mountain pass can slow the progression of a large army. This will can give you time to train, move, or heal units as well as pelting the enemy army with projectiles.
Use Waypoints to save time
When the battle is not directly near your training areas, migrating newly trained units can take some time. Waypoints can automate the repetative process of moving units. Set waypoints to bring units to the general area of a battle.
Try to research technologies if you have spare capacity or in a large map. They will pay off in the end. A Blacksmith or Advancements Centre is very useful. You can delete them later to free up space for training units.
Logistics are the most important part of a battle. Try building roads, bridges, transports, wagons, and factories (especially mines, as they are not limited by TC number) when you have the time.