Follow these steps:

  1. Read up on focal length to understand camera lenses.
  2. Play with Sketchup and the Camera > Field of View setting.
  3. Draw simple forms (cube, sphere, cylinder) with different focal lengths / amounts of distortion, from imagination or with reference in Sketchup.
  4. Find photographs with interesting foreshortening and draw the objects as simple geometric forms by tracing on top.