1) Settlements that take part in armed rebellions will be exterminated. Those who defy the imperium will not be tolerated.

2) Do not kill retreating enemies. It is dishonorable to kill a man behind his back.

3) Garrison every city. It is rare that the enemy sneaks behind the frontier but it can happen. Always protect every settlement you have unless you are conducting the scorched earth policy.

4) Do not camapaign during the winter months.

5) Show respect for the enemy culture. Brutulising the subject people is not a good way to earn their loyalty. Leave all enemy buildings standing unless you wish to replace the administration.

6) The firstborn prince will always assume the purple. Also, do not adopt foreigners or family members of a family who has previously been bribed.

7) Generals who loses 2 major battles or 1 army (at least 1800 strong) will be executed. They will charge the enemy line and die fighting in battle or be put on a ship and sunk.

8) Make extensive use of spies and diplomats. A good general will scout the way ahead and not rush blindly into things. Make sure to maintain good relations.

9) Instate puppet rulers over cities which are friendly and have been hostile because they were following orders from their king.

10) You cannot adopt anyone from the royal family. If the royal family dies out then the next most powerful family takes over. Then they cannot adopt anyone who have the new royal family name.

I usually play parthia so ive made houserules to fit their gameplay.