Unlimited movement:
Group several of your archers, horsemen or soldiers together and select the group. From the troop menu, click "Divide", and the troops will spread out onto adjoining squares. Click on the trooper nearest to your destination and click "Enroll". The whole squad now join him on that square. Keep repeating this until you leapfrog your way to the enemy city. You can use the "retreat" trick mentioned above if you need more action points.

Unlimited bombardment:
Load a cannon onto a ship and set sail for an enemy city. When you arrive on the coast, make sure the boat has at least one action point. Click on the boat and click "Unload". Select the cannon. The cannon will arrive on the beach with 10 action points. Blast what you want to, but do not move the cannon away from the boat. When the cannon is down on action points, put it back on the boat. Select the boat, then unload the cannon again. It now has another 10 action points. Repeat this as many times as needed, with multiple cannons. This also works all the other military units, including wagons.

Build large army:
When you recruit a settler into the military, he is still a resident of your city and the house owned by the settler cannot be used until he is dead. The answer is eviction. When you conscript someone into the army, destroy his house. Then, simply have an architect build another house in its place. This enables you to recruit more and more people without housing restrictions. The result is an army of 204 year olds with very gray hair, but they still fight great.

Good morale:
If you are foolishly democratic and allow your soldiers to have houses, you may notice that when they are injured in battle, the "Death to the Captain" thought bubble appears over their houses. This tends to upset the whole town. If that happens, execute the soldier by having an archer fire on him, or better yet a cannon. Bribing the church is a good way of keeping morale up. However, do not overlook the more economical option -- if someone has low morale put them in the army. Once the person is outside the barracks, execute the traitor as described earlier.