Begin by sketching the outline of an object and then ruling blue horizontal lines across the piece of paper, stopping at the edge of the object, simulating the lines on a page. Contour lines are drawn curving up and over the surface of the object, with tone added to help emphasize the form of the object.
Cross contour drawing exercises are great for helping strengthen your observational muscles. And when you start shading your mark-making will be that much more believable as a result. Watch the video below for some cross-contour exercises that you can have a go at today.