When I was in art class in high school; many, many years ago, one of the most talented people I ever met, my classmate Scott, drew a kid skateboarding completely from dots. I thought that was some cool s%*@. Some years ago, I drew my first pixel drawing. Not as hard as I thought it would be, of course after I figured out how to do it. My first try at this was the Warrior Princess drawing.
First draw image with pencil very lightly.
Next, with fine point sharpie, dot the image on the pencil lines.
Erase the pencil lines.
Start dotting the image with sharpie, shading areas to give dimension.
Where there are areas that you want to be darker, like the hair behind arm on the left, mark dots as to almost coloring it in completely but strickly with dots. Use more dots where you want the dark areas and less dots for lighter areas. Keep in mind that this is permanent marker so take your time and plan your dotting before marking them.