Setting archers to the sides might also help. Especially if they are set to fire at units which also tend to be set to the sides (flanks) of the battlefield).
But Kristoffer (one of the developers) had very definite ideas about the effectiveness of telling your archers to fire over the top of their own units to hit units they cant see. I guess thats one of the drawbacks for having a teacher of mytho-religio history designing the game.
Also, a note on some of the previous posts. There is supposed to be a difference in the game between the ideas of rout, flee, and retreat. They are not meant to be interchangeable in the conversation. As I understand it, Retreat is the one that stops to try and make a decent choice.
