Play conservatively. Order your troops into line formation early, and attack only when you feel confident that you'll win. Most actions cause disruption, and a highly disrupted unit is worthless, so be sure to stack the odds in your favor before committing your men.
Keep your cannons out of the front line. Sure, it's tempting to mow down the enemy infantry with them, but cannons are easily captured if assaulted. You'll miss them when they are gone.
The prime target for your cannon should be the enemy cannon. They are the most destructive unit on the battlefield, and deserve your immediate and repeated attention.
Make sure you keep a leader's charges within his command radius. There is nothing more frustrating than wasting a unit's turn because it is not within a leader's command radius.
