Draw your basic design outline in pencil. Use a hard lead pencil and make light strokes so you can easily erase any mistakes you make.
Outline the design with a black marker. Apply more pressure to the marker in areas where a bolder outline is needed. Vary the width of the lines to create the illusion of depth.
Block in the design with colored markers, applying ink in a circular motion to prevent visible stroke lines. Start with the lightest tones, which will be your highlights in the finished product.
Decide where you want the direction of light to go in your drawing. If you are unsure how light affects solid surfaces, shine a light on a three-dimensional object to see where the light and shadows go. Notice that the object is lightest where the light hits, with shadows on the side opposite the light and mid-tones on the sides.
Block in mid-tones by applying another layer of ink over the original colors in a circular motion. Layer color from the same marker or a slightly darker version of the same tone. Leave the highlights (the original color) intact where the imaginary light hits your drawing.
Apply another layer of ink over the mid-tones in shaded areas of the object. Shaded areas logically go on the side opposite the direction of light, as well as in wrinkled areas, such as fabric folds. Use the same marker or a slightly darker version of the same tone to apply the shadow layer.