This video explains what the specular parameter is in the materials dialog. This will help you to understand how to use it, along with the Smoothness parameter which influences it.
Here are two videos which show how to control the lighting in a scene by adjusting several material channels. The diffuse and ambient amount channels govern how much light is absorbed or reflected back to the viewer. These videos show how to use them.
Quickly create a shape to generate caustics.
Note: For users with Strata 3D Design SE or CX
This is a two part tutorial that walks through an interesting little projects which helps to demonstrate some of the render dialog settings. It specifically discusses what is called radiosity or global illumination and some settings that control this function.