Hail to ye all.

To be honest my battle formation often varies considerable based upon the units I have availible to me, the terrain, the weather, and the units I am facing.

On a flat plain, with the army of my choice, I would have archers in front, spears behind with light infantry on the wings, medium and heavy infantry behind the spear wall, along with another unit or two of spears to plug holes or spoil flanking cavalry. I'd also have a unit or two of archers behind the spear wall, in order to continue laying down fire while my front line archers retreat behind the wall. As for cavalry... I'd have a unit or two of light cavalry for dispersing isolated missile troops and for pursuing broken foes.

I have found one useful manouever to use with this type of formation: If enemy spears or light infantry engages my spears on the front of my line, I will place my engages spear unit on loose formation, charge my medium or heavy infantry through my spears, and as soon as they open up a pocket in front of the line, return my spears to close formation. Sure, my spears take increased casualties for a moment or two, but it's faster than marching my swords around my flank, especially if the enemy heavy hitters or cavalry are on the flank. This way, I can break the enemy center and watch the foe crumble from the center outward, especially if I can get two or three units through my line at the same time.