Use Call to Arms
Many newbie players do not use Call To Arms when their town is under attack. If the enemy attacks your town and you want to deal with them quickly, push the Call To Arms button on your Town Hall. Then command the Militia to attack the enemy. Don't chase them too far, return to work if the enemy is clearly running. Build towers if the enemy continues hit and run attacks. Towns should usually have several towers protecting them anyway.

Masonry
Humans can have the strongest buildings by researching the Masonry upgrades in the Lumber Mill. Keep in mind that those upgrades will also make your Towers tougher so you may want to research those upgrades for stronger towers alone.

Use Towers
Build Towers and use buildings and Farms to surround them. This will make it harder for enemy Melee attackers to reach a tower but it will also make it harder to repair a Tower. Build at least 1 Arcane Tower at your expansions to protect them.

[ Click to Enlarge - 181 KB ] Human player Hello defends against a TillerMaN attack.	[ Click to Enlarge - 195 KB ] A Human player defends his expansion with a Guard Tower and Arcane Tower. Many Human players build at least one Arcane Tower at their expansion.

Speed Build
Multiple Peasants can be used to create a building faster than using only one Peasant. Just select some Peasants and right-click on the partially-completed building to speed up its construction. Human Peasant power building costs more resources for each additional Peasant used.

It takes 2 additional Peasants to double the rate of a building, 4 to triple, etc.

[ Click to Enlarge - 184 KB ] Peasants repair-build a Town Hall very quickly.