What is the most important factor in civ game ? Growth, right?
So i built my city strategicaly to grab at least 1 food bonus per city, and i dont over lap too much. 2-3 tile per city maximum, most of the time no over lap at all. But it depend on map size, small map, more overlap, std map size, few overlap.
You will be surprise what just a fish tile on a coastal city could be a very powerfull growth factor with a harbor, then you can assign a citizen on that nice golden mountain close by...
Dont forget that if you cut forest and irrigate a game tile( exept on tundra), it is also a powerfull food bonus.
So basicaly, food bonus tile give initial boost to growth, and later when the city size is topled, it provide enough food to exploit high production tile like mountain and hills.
Second factor is river and small fresh water lake, no aqueduc, like already said.