Value Scale
A value scale (or grayscale) shows the full tonal range of a color. The value of a color is its lightness to darkness regardless of the hue. Value is more important in creating convincing form rather than the reliance on color. It is the most important design element of a drawing/painting.
Without an accurate value plan, your work will appear flat. Good value structure is very important to the success of a painting. When you explore a picture in a gallery, value will dominate your visual experience - it is the strongest element in the drawing/painting.
To easily see the value structure of a drawing/painting or scene, squint your eyes until you are looking through your eyelashes - you will see its value better.
Recognizing value does take some practice. Another way to judge the values in a painting is to look at it in dim light or moonlight.
11 Step Grayscale : See the value scale below. It is divided into 11 steps and must include whit and black.

These are pencil strokes showing the textures that can be created by varying the pressure when applied to the paper and varying the distance between the strokes. Some strokes will be used to create tree bark, grass, barn wood cracks etc.