My usual full-stack setup...

1 General
2 Light Inf
1 Grenadier
4 Arty (usually howitzers)
4 Cav (usually Lance-based)
8 Line Inf

Occasionally I substitue the Light Inf for Line Inf.

4 units of LI make the center of my line. 2 units are placed at the flanks, slightly 'staggered' behind to respond to any cav attacks or as mobile reserves to divert to the center when necessary.

My artillery is spread out along the center although I occasionally concentrate them in the center if I am able to find good ground to deploy my army on.

I keep my Grenadiers as my shock troops/elite reserves while my 2 units of Light Inf are either placed at the flanks or center to provide harassing/supporting fire.

Naturally, my cavalry are at the flanks.

Early on, the enemy will throw his cav at my flanks unsupported, running into the line of fire of 3-4 of my line inf. Naturally, theyt are cut down very fast. With that done, my artillery can proceed to pound the remainder of his army, and this usually forces the AI to throw everything in a disorganised manner at you.

Some semblance of tactical competence the AI has displayed to me is that it has successfully created a gap in my center before by concentrating its attack against one or two Line inf units of mine and breaking them...before my flanks show up and crush them.

Once the center is engaged, my flanks of light inf and 3-4 units of line inf are free to wheel around and blast the enemy from the rear.

During siege assaults it sub my howitzers for mortars. For some inexplicable reason, the AI will abandon the entire fort and attempt to attack you directly in a very disorganised manner once you start barraging them. Add the observation that the AI loves to gather everything in the center of the fort before it assaults you and you get a big massacre in the middle. As units stream out from the fort towards you in a long column, its no wonder they are routed back not long after.

If I must assault I shell sections of the fort, forcing the AI to vacate these sections. Following this I move in my troops to scale these sections and regroup.