Cigarette buts, broken bottles, McDonalds bag, newspaper and so on add a lot to realism. All these little things are really easy to make. Do a basic shape, throw noise modifyer on top and you are done. Leave the rest to the textures. As for bottles, just create a spline profile and slap Lattice modifier on top.
I only modeled the visible parts. No need to spend lots of time on objects that will never be seen. Also, the farther away the object is in the scene, the less details you need.
Lamps & Signs
These old lights weren't as easy to make as one would think. The tall one was made with Lattice modifyer and the rest was polymodeling. Same applies to wall lamps. Sign is pretty basic apart from the little wavy details. I used renderable splines for those.
Most of the textures were made using the Blend material and Composite materials. Composite lets you mix together more materials into one where as Blend blends two materials using a mask.
Example: Road Texture
Road texture - Blend material - road texture from the CD plus some dirt
Road stripes - Standard material - found the stripes on the internet and added some dirt.
Final road texture - Composite material - road texture is the base material and road stripes as material 1. What this enables me is to move the stripes texture freely on the road using the UVW Mapping modifier. I can place it wherever I want, I can stretch it and rotate it.