Difficulty: Moderately Easy
Step1
Start up your human economy. If you've played any Warcraft, Starcraft, or other craft game before, you probably know how to start as the human town. Send your peasants out to mine gold and chop wood and pump out more peasants to do the same. Once you near max capacity, don't forget to build more farms.
Step2
Build a lumber mill to increase your harvesting and to enable the building of guard towers if you're likely to be attacked in the early game. If no serious attacks are coming, towers might let you hold off on a barracks for a time, but do not neglect the barracks for too long; you will need an army eventually.
Step3
Upgrade your town hall to a keep ASAP and build a blacksmith. You'll want a castle eventually, but the blacksmith will let you upgrade armor for your troops in the meantime, and let you produce riflemen. Your upgraded footmen and riflemen should hold off the enemy until you can upgrade to a castle and start producing knights.
Step4
Tower over your opponents. Humans have very strong towers, especially if you purchase the masonry upgrades at the lumber mill. Surround your towers with farms so ground troops cannot easily attack them and they will do most of your city defense for you, freeing up a large portion of your troops to stay on the offensive.
Step5
Magic is power. The humans have some powerful spellcasters on their side, especially the archmage, who can teleport whole groups of troops at once. Use mass teleport to drop a full compliment of siege engines into an opponent's town, or to rush your army back home to bolster your tower defense.