You should read the excellent PSG Art Tutorial

PSG Art Tutorial

Arne Niklas Jansson’s mini art bible has been around since 2005 and still hasn’t gotten old, simply because it’s a fantastic high-level overview of materials, color, lighting, and all other sorts of drawing and rendering tips.  It’s full of example images, defines all the technical words it’s going to use up front, and is an all-around amazing art introduction.