z overview

If you press Z in a battle you will get a large overview and can easily get a grip on where the fights are happening

and where the enemy tries to flank your team.

controlling your units while dead

If you die you can still order your units to follow the person you're spectating or to attack.
This can prove very useful if you need them to fall back or attack something instead of bracing.

Combine this with the Z overview to pick someone far back on your team and C to follow
if you want them to retreat out of harms way.

Stamina bar

Your stamina bar will only regain stamina when you are not holding down shift, the same goes for your horse.If your stamina bar hits 0 it will take a couple of seconds before it starts regaining stamina again. (this is not the case for your horse) So to maximise stamina try to stop sprinting when your stamina bar hits close to 0 and watch it replenish some before you start running again. 

Trebuchet

When aiming your trebuchet green lines means 90% to hit red lines means 90% to miss

max range of your archers

If you have an archer unit that has the aim at area skill you can press it without activating to check your archers general range

spying on your enemies with the cannon

After you shoot press Z to follow your shot, that way you can see the location of your enemies clearly.This will help you gather information for your team and your next shot.