A drawing, a painting, a photograph devoid of any colour. Essentially it is black and white only (not to forget all the mid-tones, i.e. grey(s)). A bit of colour theory of hues and value, not so much chroma for obvious reasons, would be an advantage. However, you don’t need to become a colour theory expert. All you need to do is to create contrast between the shaded areas and the lit areas. Personally I love stark contrasts. Figure out where the darkest shadow and where the highlights lie. From there, you tint your paper for the shadows and go easy on the highlights when you draw on a lighter or white background. On a black background (which I prefer), you erase out the shaded areas or use charcoal and draw the highlights.