Commissioned into US Army Field Artillery I wish to add a few minor considerations to your excellent start. Before I begin though, understand that I consider combined arms (the use of Infantry, Cavalry and Artillery simultaneously) as key to victory. These comments assume the reader has zero knowledge and are not meant to insult those of you who have greater understanding of the topic.
As simple as it may seem, take time to position your artillery on (usually high) ground with broad uncluttered fields of fire. Actually zoom in on the spot and look from a “grass-top” view. My Cavalry have successfully wiped out enemy batteries while sustaining no casualties. This is done by using a covered and/or concealed (C&C) approach until the Cavalry break forth in an earth thundering charge and sweep away the startled enemy. Cover protects you from direct fire. Concealment hides you from, but does not stop, direct fire.
I have also watched AI deployed cannons lay waste to the hillside directly in front of their position. Learn from the enemy.
Overlap your fields of fire. This is known as integrating the defense.
Additionally, scan projected enemy C&C approaches to you. I once had the unpleasant occurrence of seeing an enemy maneuver toward me through my town. My supporting artillery fired through and destroyed a named building (which I then had to spend gold to repair).
These are the 1/3rd – 2/3rd rules:
Defense = Artillery range covers 2/3rd of your territory. The enemy will come to you.
Offense = Artillery range covers 2/3rd of your enemies territory. You will go to him.
Position your artillery in the rear of your deployment zone. This usually keeps them out of immediately deployed enemy cannon range. He will have to displace forward to use his cannon. If cannons are moving they are not firing.
Position your artillery in the front of your deployment zone. If this occurs, engage the enemy cannon as first priority. Fire your artillery at the enemy cannons and mount a Cavalry flanking movement (or Infantry if you have built poorly and do not have at least one Cavalry unit per army). In this gaming environment units cannot fire in multiple directions simultaneously. Having the Cavalry use a C&C approach will generally bring you within close range of an enemy battery before you initiate the devastating charge at the enemies flank or rear. Do not charge the front of anything with anything unless absolutely necessary. Oddly enough the AI program rarely leaves behind a local security unit for its cannons.
Position the artillery behind a wall if possible, noting if you can actually “see” over the wall as addressed in Employment above.
Do not position behind a building, hill or forest except in unusual situations which I shall not address due to their exceptionally rare occurrence.
Station an Infantry or Cavalry unit nearby for local protection. I prefer Pike formations during the opening phases of a campaign as the highest threat is generally from Cavalry. Pike formations are generally worthless in other situations or used for a desperate reserve, but that is merely an opinion, not fact. Any unit is better at melee than a gun crew.
If you maneuver in the line of fire of your artillery your men will die. Do not forget to lift and shift the counter-battery fires you have on the enemy cannons before your Infantry and/or Cavalry charge slams into them. This applies to musket fire as well.
There are only two reasons to move your artillery:
Every other reason is overcome by accurate and thoughtful initial positioning aimed at maximizing indirect fire duration and effects on the enemy.
If you have to abandon the guns (for shame) do so in a manner that allows your gun crew(s) to retrograde (flee) behind the unit you have sent to cover their movement. Then, once the enemy is driven off, go back and re-man the faithful guns you so shamefully had to abandon.
These are just some of my thoughts and considerations. Thank you for your original thread as a solid entry discussion.