I've been playing head to head with a few friends of mine, and I wonder if other people out there make up rules for the campaigns.
The rules me and my friends usually use are as follows:
You may only play as the AI when it's an ally of yours.
You may never autoresolve unless autoresolve predicts you will have 99% or 100% of your army left. (It's time consuming to play small battles.) This does not apply to battles against each other's allies though.
Before we start fighting each other directly, all pc controlled factions must be controlled by either one of us. However, you may use your armies to help with the defense of allied cities.
The capital may only be attacked when it's the only city left.
No reloading older saves unless the most recent one is bugged.
So, what rules do you play by? Or do you only adhere the one rule; "there are no rules"?