I play as Persia/Rome so I can get a powerful offensive unit early (Immortals/Legionary) then provoke a war with the largest civ closest to me in the ancient age. The key to all of this is NEVER trading my maps. It pisses off the other civs and, more importantly, if the enemy doesn't know anything about you and you know the lay of their terrain, you have a distinct advantage over them, ie build a few horsemen and take out their iron, horses, and luxuries. I know where they will attack and build up my army on their border. This way, I usually double the size of my empire to the optimum number of cities (corruption stays low). I concentrate on culture to capture the other civs border cities and amassing a fortune so I can upgrade my military, build improvements, and buying techs (science is set at 20%).
Later in the game, after I get rifleman, it gets real easy to provoke my neighbors again because I'm the Big Dog on the planet and everyone wants to screw with me, so I make 'em pay for their insolence. Before I go to war I build a settler in my largest cities and then slash and burn my way through enemy territory. If the city is a money maker (lots of river/coastal squares, resources, trade goods) I keep it. If it's not I raze it and plant a settler. Any left over settlers join my new settlements.