Play usually as France or England, my formation looks like this
----HC HC ------S S HI HI HI HI HI HI S S ------HC HC----
-------------------HI------S--------HI-------------
-------------------A--A----A_----A----A-------
------------------------G-------------------------------
Where S = spearmen, HC = heavy cav, HI = heavy infantry, A = archers
Don't usually use HA, but if i were using them, they'll be placed on the flanks ahead of the HCs