Find an interesting three-dimensional object (a sculpture, a bench, or really any interesting thing). Carefully look at it. Move around it. Identify the most interesting elements: look at the edges, surface, shape, material, size, texture, subject, etc.
Using a pencil, make a contour line to define the edge. Use shading to add dimension. Go slowly and keep looking. Darken lines you feel sure of. Trust yourself to add anything else you feel is important.
You will know you’ve done it right if you know something more about yourself or the object you drew.