Hulaku,

What I do is make my whole army formation first either by dragging out small groups or using one of the army group formations. If you've made small groups, define them with hot keys. I then CTRL-A and group the entire army. While holding ALT, I position the entire army with left mouse click on the map and then rotate it with right mouse click. This method positions and rotates the army about what looks to me like the center of mass assuming each unit has the same mass. At some point before you actually engage the enemy, you want to ungroup the army and operate with the smaller hotkeyed groups. I'm able to setup and move my army very quickly this way. Also, if you have similar units such as two feudal knight cav on each wing, place the left one using the left unit icon and the right one using the icon to right. That way you know the left most icon is the cav unit on the left flank and the right icon is the one on the right. You can do the same thing with small groups and the hot keyed groups. Positions of units within groups is a much more difficult thing to sort out, but you can visit tootee's Shogun Academy site for an explanation of how the game places units within a group.