- only play in the huge universes to give the AI time to spread
- AI gets 'agreeable' home systems
- never, ever buy, sell, or trade tech. You want it, get off your lazy ass and research it yourself.
- expand to predefined borders and STOP. Let the AI expand all around those borders without impeding it.
- use the slowest tech games so that it isn't really possible to get a huge tech advantage over the AI (e.g., 990k setting)
- use victory conditions which require conquest (e.g., 75% of economy, 75% of population, 50% of colonies, 100% of all three). It's too easy for a human to game the non-conquest victory conditions.
This results in really slow games, but I'm a builder who likes staying at peace for as long as possible so this suits me just fine. Also, because I research ALL THE THINGS! and don't trade tech, sometimes the AI gets a local advantage in certain items which proves problematic during a conflict (e.g., they have much better weaponry). These are also huge empire games, where getting from point A of your empire to point B of your empire can take months, so the tactics and builds are different than those of smaller games. It's quite easy, for example, for a smaller empire to do considerable damage along the border before a significant fleet presence can get to the trouble area.