The following are some exercises that help you develop your ability to make forms.
Exercise: Making your own forms
Waste some paper on this. Draw some forms that you have been taught (such as a house, an apple, a tree, a person.) Now make some forms of your own. (Don’t try to be perfect.) For instance, make a vase, a window, a hand, a dog. Now go look at these and other forms. Now show your drawings to someone and ask what they remind them of.
Hard and Soft Edges:
Forms exist in space and often, the depiction of a form on a flat canvas is the first step towards creating the illusion of space. Here is where you need to start to observe carefully the use of contrast and line to create edges. A hard edge (created with a lot of contrast or a hard dark line) makes an object appear crisp. But a soft edge is particularly helpful in creating the illusion of a round object. Also, hard edges seem to come forward while soft edges recede, increasing the illusion of depth.
Exercise: form (monochrome)
Set up a still life consisting of some very simple thing or things, preferably white or off white, such as a couple of eggs or a cup and saucer. Set up the light so there is a strong directional light. Paint or draw with attention to the roundness, the edges, the places where the form is lost and light flows through. I want you to see that form is defined by edges and you can control the composition by using the edges to allow the eye to move around the painting.
Basic or home value
There’s another aspect of value that is helpful in starting a painting. Some refer to it as “home value” or basic value. It’s easiest to see if you look at an object that is all one basic color or value, like a cup. When you shine a light on it from a direction, parts of the object become darker and lighter. An approach to the object is to first establish the “home value” and then to lighten and darken the object (and, of course, the space around the object) according to the direction of the light source.
This exercise gets you to find the "home value" or basic value of a subject and then lighten and darken it. The exercise should be done with paint, using only shades of grey or brown. You can use burnt umber and white or black and white or a combination of blue and brown and white. Set up three objects, one light, one medium, and one dark, in front of you. Paint the basic value of each object, so that it is all one shape. Then, if possible while the paint is still wet, start developing the darks and lights on each object, working out from the "Home value". Notice that the light object will be all in the light shades of grey. The medium object will be all in the medium tones and the dark object will fall all toward the darker tones of grey.