Hi,
1. If you are attacking with Modern Armor, it is possible to reach all this in the first turn. You can even not dream about contacting the AI in the same turn, when you declared war! You have to wait a few turns or eliminate him (as Master Zen already wrote).
2. Again, I can only aggree with Master Zen.
2.a.) My strategy is to decrease the size of the city DRASTICALLY in a few turns, by picking up the workers (in the city window). In the first few turns, there is a resistance in the city anyway, so why to feed them

?!?! Simply, make entertainers from all the workers.
2.b.) Later, when the order is restored and the resistance ends you will have less unhappy faces.
2.c.) When the resistance is over and there is no civil disorder (yet), buy some nice improvements, like Temple and Cathedral.
2.d.) Later, if the people in the conqered cities (or even in your motherland) are still unhappy (or beginning to be) you have to play with your luxury slider or buy some luxuries.
2.e.) Be sure, that the new cities are connected to your capital, so they can enjoy all the luxuries, that you core cities enjoy.
2.f.) If you reached the point 2.d.), you can contact the AI to offer him a peace (enough turns has been gone from the beginning the war)
2.g.) The number of units stationed in the newly conqered cities should be only enough to beat the resistance. The best units should wait/rest outside of the city.
2.h.) You can also make an "ethnic cleansing". Make some settlers in your core cities ("ethnic clean" cities) and join them to these "ethnic foregn" cities.
hope this helps
cumi
EDIT: The "wiping out completly" strategy is also very considerable, when none of the strategies above helps.