PersianImmortal
Warlord
When at war with your neighbor (which i'm always) attack with a settler shielded with some defenders and a good attack unit... plop down a city the moment u find a convenient spot inside enemy borders (much harder than it appears); preferrably further away from your border and in the same turn sell it to an advanced civ (preferrably on another continent) for loads of tech and money.. (AI's overrate cities.. even crappy ones).
In a few turns the city goes back to u're enemy .. u've lost two citizens but have made the necessary tech advances u couldn't make due to being in war (or mobilized for war).
Repeat.
In a few turns the city goes back to u're enemy .. u've lost two citizens but have made the necessary tech advances u couldn't make due to being in war (or mobilized for war).
Repeat.