[vfb]

You want at least 5 units in each squad to prevent automatic morale checks that happen for squads of 4 units or less.

If you expect to come under large area-of-effect attacks, including arrow fire, and your units have good survivability, then you might want to create squads of just six units. I don't like squads bigger then 12 units usually. Maybe if there was a formation other than "Big Square" ... but that's all we've got for now.

Splitting your army into large amounts of small squads also helps prevent clumping on a single target, where you've got a bunch of melee guys who are just dancing around not hitting anything.

I try to spread my army out over the field, with nearly all melee units except bodyguards on "Attack Rear" or "Hold and Attack Rear". It's not that I'm actually trying to attack rear, I just want them to march forward and get into battle. If your army is one big blob, enemy ranged attacks will have an easier time hitting the blob, because even when they miss their target, they'll hit something.

If you are just playing SP then a small group of shieldmen is an excellent archer decoy. You can even place their commander alone in the backfield on holdx5, and have the decoy "Guard Commander." The enemy archers will run forward so they can shoot at these decoys since they have locked onto them as a target. They'll spend a couple turns without shotting anything sometimes, and run right into your melee units. In MP you probably want some wounded archers to place on your frontline since other players will give "Fire Archer" orders.