Points are scored for possession of monuments, sea areas, and for relative strength of control of various areas of the map. Areas are worth varying amounts depending on the epoch. For example, control of Sub-Saharan Africa is worth nothing until the final two epochs. Points are scored at 1x, 2x, and 3x the area base value for these levels respectively. Points are scored not only for the regions controlled by the empire played on that turn but for any remnants of empires from previous epochs.
Empires vary widely in the number of units they can field in a turn.
From four for the Incas and Aztecs to 25 for the Romans. Which empire you play in a turn is determined partially by random drawing at the beginning of the turn. The player whose combined total of empire unit value is the least draws a random empire first. He can choose to pass it to another player of his choice or keep it. The next player then does the same until all empires have been chosen.