There are several things that some players to not take into account that are very important. First, you need to conserve as much resources as possible. Your economy is the basis of your entire empire/city/town/village/etc. Without resources, you cannot field an army period. For instance, if you are having villagers getting food from sheep/deer/boar/, DO NOT slaughter several at once. It does not bring in food faster if more are dying at once. All that does is lower the amount of food you receive as some is lost to rotting. Instead, have a large group of villagers getting food from the same animal. On a boar, that can save as much as 35 food. Another simple way to conserve valuable resources is this. If you know beforehand where you are going to build your walls, build you gates first and then build your walls around them. Don't build your walls first and then build your gates on top of them. This wastes stone, which is the most valuable resource in the game. It is very limited and most of your defense is built with it. A third way is if you have time, DO NOT use onagers or trebuchets to clear trees. Use villagers to cut them. It is slow and tedious, but it will pay off in long games. Wood is the foundation of your army, as towards the end, your main income of food will be through farming. For farming, you need a good supply of wood. From food comes gold, as in long games in which you have allies, you can make trade carts to gain gold. Both wood and stone(especially stone) must be used wisely since the is no way to get more than what is on the map except through market trade. This gets tedious and expensive when you end up paying 100 gold for 15 stone trying to get enough for another castle.

Another thing that is very important is to play to your civilization's strengths. If you are the Britons, focus on building an army of advanced archers. If you are the Huns or Mongols, focus on cavalry archers or light cavalrymen. The Franks should focus their resources on developing their cavalry and the Turks, Japanese, Koreans, and Spanish should focus on gunpowder units. The Aztecs should develop their incredible monks and foot soldiers. The Goths should work mainly with infantry units and the Saracens should develop their awesome anti-cavalry(camels and mamelukes).