My sketchbook and all of the drawings in them are the heart of my work. I keep several sketchbooks going at the same time. Most of them are dedicated to making quick drawings that record a moment in time, while others are the home to those fleeting ideas that must be scribbled down before they escape.
They are sort of a refugee camp for mostly terrible drawings and lame ideas. However out of this compost heap of drawings, grow the ideas I want to develop and nurture. Most of the drawings in my sketchbooks are completely disposable. If I don't like a drawing, I simply start a new sketch or draw or paint right on top of it. In these book, I also have the chance to try new mediums and approaches. I try to embrace experimentation and avoid fussing over technique. The funny thing about sketchbooks is, while I consider the drawings in them disposable, as a whole entity, they are my most treasured belongings.
The top two images are from my sketchbook. They show a progression of how I tend to develop an idea. The bottom image is the finished painting, done on Strathmore 500 Series Illustration Board.