Zoning is one of the most important things in Simcity. Differing zones do differing things; residential increases population, commercial gives jobs, buys goods and sells things, industrial creates pollution, goods and jobs. However, to manage them, you must know a bit more about them and what can affect them.
When placing residential, it depends on whether you want high wealth, medium wealth or low wealth people to move in, and in high density, medium density or low density.
The more the land value is, increased by various amenities, the more likely higher wealth people will move in. To push low wealth to medium wealth, a couple of parks and basic services will do, such as schools, police, etc. To go from medium wealth to high wealth though requires a lot more of that; better parks, nicer streets, uninterrupted garbage disposal, and generally everything the medium wealths want, but in a higher level.
Density, on the other hand, is a lot harder to manage. The density of a road allows buildings to increase density, and so a low density road will support only low density, medium density supports only medium and low density, etc. It increases slowly over time with happiness, and is shown in a bar. It is also driven up by high desirability, or low zoning, even for low wealth.
Location is also a serious issue. Industrial is ugly, polluting and generally undesirable, and so residential will not want to be near it. This applies more as you go up the wealth ladder; rich people can afford not to live there, but many poor people cna't. Commercial dislikes it as well, but not as much, especially when low wealth. This means that a city may have to be segregated, or even a separate city made for the industrial, in order for happiness to go up in various areas, though remember, if it is too far, commute timnes will go up, and people will get annoyed as well.
