I sketched my guitar on a piece of drawing paper then I put a piece of tracing paper over the sketch. I started drawing circles on the tracing paper following the sketch on the paper under it.
step 2 of 3
When I finished drawing the circles, I got rid of the paper with the sketch and started to color in the circles. When I finished coloring on the front, I started to outline the circles in black on the back of the drawing.
step 3 of 3
I colored all of the negative space in using black (and on the back).