when you make your civilization ,you should always make it secure by constring walls so 
that the enemy cannot come inside your civililation.try building keeps,castles and murder 
holes near your walls so that if enemy comes near your society he gets killed by the attacks 
of these.you should not usually keep on attacking the men and buldings inside the enemy's 
civilization as they can produce no. of buildings and men again and again as the have 
unlimited resources. so send your vilager inside your enemy's civilizattion and construct 
walls as enemies don't kill your villagers. you can therefore kill the buildings and men 
inside the wall. In this way you can win territories and also destroy enemy.