There are many strategies which are possible in age of empires from harassing the other person constantly, to being extremely defense, to launching large scale military invasion after a long time.

My favorite strategy out of all of them is the constantly harass the enemy with small level invasion in the early stages of the game. I will send one or two villagers out to a corner of the map near the enemy’s base. The villagers will then build just one stable near the base but slightly out of the enemy’s range, so they don’t know that the base is there. As the civilization that I play, Byzantine, I will get an upgrade which allows me to gain gold whenever I kill enemy villagers as well as get a buff against enemy villagers of +2 damage. I will then make small groups of five horses each. I will send these horses along the back rank of the enemy village to take out their villages, mostly targeting food creation. Most of the time people put defenses at the front of their base so my horses won’t get attacked and their military will have to travel from the front of their base to the back in order to kill my horses. This causes a large amount of panic on the enemy and also prevents them from creating resources which stops them from creating more military. Meanwhile at my base my economy will be thriving as the enemy won’t attack me while they are protecting their own base. I then continuously make stronger batches of military and abuse them until they discover my operation where I am creating my military and destroy it. But by this time, it is too late, and I will be far superior to the enemy in many ways.

Although all strategies have their advantages and disadvantages, I find it the most fun to constantly harass the enemy players.