Very closed cities connected by roads. (later Rail make huge power to You.)
Focus TECH development.
Playing offensive strategy with strategicly placed strong defensive cities.
Having embassies to see what they are and Stealing their TECHs.
Sabotaging cities by Diplomat directly or indirectly.
- directly: buying their cities
- indirectly: buy their unit and then use their unit to make damage (like attack setlers, or pillage).
---> so enemy is going on you with catapult, you buy it and use it against his other units. by this way you disturb his all action and set him back for while. To give you time get ready and make offense.
NOT overpopulate cities by too much fucusing on costly happiness buildings rather build more settlers and more cities to support more units.
If you can't grab enemy's city make harm, pillage detroy his settlers.