Crisp, ink-like foreground lines. Background elements made from looser and lighter marks. High contrast between black and white. Texture of shadow changes depending on surface cast upon.
Contrast between white space/block colour and heavily textured pencil elements. Accompanied by watercolour/ink.
His book 'The Snowman' was drawn using pencil crayons. Contrast of light and heavy marks.
Light and heavy marks, bold colour.
Dark marks, combination of hard and soft lines. Use of eraser to produce white space an contrast.