If your target is only a barracks, do not forget it may be a fortress by the time you reach it in combat, as fortifying comes before movement. When you are attacking a Fortress, if circumstances allow, try to avoid committing cavalry unless you have overwhelming odds. Cavalry will suffer the same losses as militia and are expensive to replace. If you are sure of victory, commit them anyway and gain some effectiveness increases.
Simulated battles are so varied as to be very unpredictable.
If you outnumber the defender heavily and expect him to put up a strong defence, waves of skirmishers at their own maximum range, shooting for 10 - 15 rounds will decimate enemy ranks and with a destination behind enemy lines, will follow through onto artillery or the rear of other lines. This should allow your main force to group up behind them and attack a vastly weakened line. The Tiralieur is an excellent skirmisher type and very cheap in economic points, only bettered by the British Highlander. Make sure your advances are well protected by Mounted artillery and cavalry if possible as well. In game 44 a large Prussian advance and a large Austrian advance met head to head and with no orders to retreat, fought for 20 rounds in a bloodbath.