Create your own grey scale

Draw a series of 11 boxes and using your #2 pencil, begin in the second box shading in with cross hatching strokes as lightly as possible, continue on to the next box shading slightly darker.  Darken your strokes with each consecutive box until you reach the last box, fill it in as darkly as possible.

Use this grey scale to observe values in the objects that you are drawing.  Notice how the value of a single plane may change from side to side.