Warcraft III: Reign of Chaos/Human buildings

Human buildings are in fact the strongest units in the game, thanks to the human Masonry upgrades at the lumber mill.

Town Hall, Keep, Castle
The Town Hall is the heart of any human base. It is the drop point for resources and is the only way to create Peasants. Town Halls therefore are the key to base building. When attacked the Town Hall can summon nearby Peasants to it to convert them to Militia, which are more capable of fighting.

Barracks
The Barracks is the standard place to train your basic soldiers. Footmen, riflemen, and knights can all be created at this building, making it a valuable target for your enemies. Also researched here are abilities for each of the three units - Footmen using the Defend ability become almost impervious to piercing attacks (like arrows and thrown axes), Riflemen have a far more effective range with their Longrifles upgrade, and Knights can take more punishment with Animal War Training. The Barracks, next to the Altar of Kings and a Farm, should be the first buildings you create.

Farm
Unfortunately, human farms don't have any special abilities like the other races' food production facilities. They can't be garrisoned or barricaded like burrows, upgraded into towers like the Undead, nor can they heal nearby allies like Night Elf Moon Wells. They also produce less food than any of the other buildings. Farms have two things in their favour - their small size (allowing you to squeeze farms in close together) and, when upgraded, their extremely strong armour. Farms are therefore often used as walls to barricade ranged units and protect them against melee attacks. The same can also be said for towers and Gryphon Aviaries (since aviaries only produce flying units, which can fly over the farms).

Altar of Kings
The Altar of Kings is what produces human Heroes. Heroes are extremely powerful units that can gain experience and carry items, much like a player character in an RPG. Like any unit, however, heroes can die. Heroes can be resurrected at the Altar for a cost - the lower the level of the hero, the lower the cost. In most games, the first hero you create is free - costing only food. Since the hero is a stronger fighter than a normal unit and gains experience, the Altar of Kings should be the first building you construct - the quicker you get your hero earning experience, the better.

Scout Tower
A familiar sight from Warcraft II players is the Scout Tower. This tower is almost completely useless. When upgraded, however, it provides invisibility detection. Its only real purpose is to be upgraded into a Guard Tower or a Cannon Tower. It is relatively cheap, so if you are hard-pressed for money you can always build a network of Scout Towers around your base to spot enemies lurking nearby.

Scout Towers are one of the few buildings that have light, not fortified, armour. This reduces the amount of damage done by siege units, but given its low HP it can still be destroyed easily by any unit.

Guard Tower
The Guard Tower remains practically unchanged since Warcraft II. Like before, it is upgraded from the Scout Tower, and it shoots arrows at nearby enemies. It causes less damage than the Cannon Tower, but it is far more versatile - it can strike both air and ground units, and doesn't have a minimum range. This makes the Guard Tower a better choice overall than the Cannon Tower, which is also more expensive.

Cannon Tower
The Cannon Tower remains practically unchanged since Warcraft II. Like before, it is upgraded from the Scout Tower, and shoots cannon shots at nearby enemies. It causes more damage than the Guard Tower, but is less versatile - it can only strike ground units, and can only strike at units up to a certain point. It also fires much slower. Cannon Towers also cause siege damage, making them effective against another human player attempting to use Siege Engines. In the end, however, the reduced versatility and extra cost make guard towers the better buy.

Lumber Mill
The Lumber mill remains almost unchanged since Warcraft II - it still is a drop point for peasants dropping lumber. However, today it also serves as a basis for two important upgrades. The Masonry upgrades are researched here, which can make humans have the strongest buildings in the game. Perhaps more importantly is the Lumber Harvesting upgrade, which upgrades the amount of lumber peasants can carry per trip. When fully upgraded peasants can carry up to 30 lumber back to base - the most of any unit other than the dedicated Goblin Shredder (which can only be created through a neutral building).

Blacksmith
The Blacksmith is the source of attack and defence upgrades for all human units. Gryphon Riders, Footmen, Militia, and Knights all benefit from the swords upgrades, which let them cause more damage. The Plating upgrade increases the ability of Militia, Footmen, Knights, Siege Engines, and Flying Machines to absorb damage. The Gunpowder and Leather Armour upgrades provide similar upgrades for ranged and support units respectively.