Controlling Victory Locations Edit
There are 3-6 victory locations on the battlefield. Besides damaging enemy morale once you control more victory locations, they grant you special features, e.g. villages replenish the stamina of your soldiers in their vicinity, and guard posts let you cast the "cloud of arrows" spell. Features granted are always pretty reasonable. You can win a battle even with a smaller army by smart victory locations management, along with reducing troop losses.
Stamina Management Edit
As units become less effective at lower stamina, raising stamina levels when leveling units and keeping stamina high during the battle itself is very useful.
Using Skills and Spells Edit
On skills and spells, both your own Knights and enemy Knights are worthy of attention. Understanding which spells are strong against elite units (soldiers are individually strong, but few in numbers) and which are strong against numbers can help you use them effectively.