I will occasionally tune up my observations skills with a contour drawing. In its most basic form, a blind contour, the eye traces slowly along the subjects edge and the hand follows, it's motion captured by the pencil it grips. The hand becomes sort of seismographic trace of the minds eye. The resulting drawing is not really the point, it's in fact not even necessary. You could use a dowel or stick. It simply is an exercise in observation and patience.
I sometimes will do a modified contour where I will intermittently look at the progress of the drawing to check how my navigation is proceeding. I can make mental notes regarding position and proportion. Something like a real drawing can result from this. I've included some modified contours from a notebook.