I usually target cities nearby that are already pretty developed. I can easily take them down if they are "NoCommander" cities. Obviously as I need them, I'll upgrade my farms and Castle; so they may be finished before their time.

Anyways:
Max out the resource-buildings
Make a barracks at level 10
Simultaneously build up the castle and storehouse (Start building an army)
Max out my farms (Still building an army)
At the same time, build up walls around the entry points. All at level 1, then all at level 2. I don't want any part to be upgrade ahead of the others.
Once I've gotten a strong resource collection, population and defence, I build a Stable and Workshop (Or another Barracks) to level 10.
At this point I should have a good sized army and resource rate.
Start building other things such as library and tavern to max.

Once I've gotten my city running (maxed out on farms, resources and military), I will start terraforming the remaining landscape. This helps for three reasons. It helps use up resources so I'm not as much of a target; it gives me an excuse to come online; and it slows down enemy movement in the city.

Hope this helped! It's worked so far for me, I'm on my fourth city!