Very important stuff. Especially, the part about keeping troops close and organized. I think you beat me our fist game tonight because of this.
One tactic I use is to try and separate the enemy with my. Cavalry. This can happen before they attack, by targeting archers. One of my favorite strategies is to flank the enemy with my cav, just as they are rushing my archers. Instead of staying to fight I get the cav out quickly and hope the enemy splits off there by weaken in their group attack. Sometime I scatter my ranged units so that the enemy might spread out to follow them.