Use different colors and styles on the structures in your model cities, even as far as to paint different colors on the same structure. These buildings were photographed in 2004 across the street from Seattle's King Dome (which is only a couple blocks from the city's main passenger station).
When you install a turntable on your outdoor layout, don't forget to provide for drainage. This G scale turntable's drain is covered with a small section of screen to prevent clogs.
When you start on building the scenery in your city or industrial areas, make some cardboard and paper mockups of the structures that you want to include. The mockups can help you determine if the structures you want are the right shape and size for your layout; if you use the DPM wall templates, you'll even know what you need to buy to build them.
Have you earned your Master Builder: Structures certificate yet? One of the structures you are required to build to earn this certificate is a bridge, but there is no requirement stated for the size or type of bridge to build. A model of this simple, small bridge in Fitchburg, Wisconsin, will do quite well to satisfy this requirement.