I belong to this great online art community known as Easel Insight.  It is a learning/ mentoring environment created by professional artists Gabor Svagrik and Phil Starke.   Artists of all skill levels become members in order to have access to educational material focused on the main principals of good painting.  These principals focus on good design, composition, value control, brushwork and color.  Regardless of stylistic preferences, except for maybe pure abstract painting, these principals are the basis of a good painting.  Of course, the concept, or subject, of the painting is important to the viewer but it is not critical to the success of the painting effort itself.  

Probably the most important aspect of these painting considerations is value control.  Most would think color is the most important element but they would be wrong.  Most paintings that are attractive to look at have a good composition that consists of a good relationship of values, or what we can refer to as the range of distinct shapes defined by variations white, black and grey.  To be successful, most compositions consist of a limited range of values, preferably between 3-5 values.  In a sunny landscape painting for example, the sky is often the lightest value so that would usually form one value shape in the composition.  The darkest value shape is often formed by the vertical tree elements and their shadows as well as the shadow side of any other objects in the scene.  The rest of the landscape, such as the land itself,  fills out the remaining value shapes.  

I make an effort to really limit my paintings to 3 main value shapes consisting of a dark value shape, a mid-tone value shape and a light value shape.  I try to make one of these value shapes the most prominent and I try to locate the greatest contrast of values in the intended focal area of the painting.  If you look at the painting I recently completed below, you can see how I made the foreground tree area the darkest overall shapes.  The foreground landscape I made a darker mid-tone value while the background mountain was a lighter mid tone value shape.  Finally, the sunlit base of the background mountain was my lightest value and was to have the most contrast to help reinforce this as a focal area.

Once I completed this painting on the left, I had called it done.  However, I submitted the painting for review by my peers at Easel Insight and as they are often apt to do, Phil did a quick paint over which you see on the right.  Phil focused on the values and how this painting may be improved by further defining the darker value shape to create a greater sense of depth and focal area.  Again, nothing about color but this value change does a lot to change the entire feel and perspective of the painting.  This is why doing limited value studies are so important to the success of the final painting.  Feel free to let me know if you felt the change is an improvement to the original piece or if you thought it was fine as it was.  My vote is for the second paint over version.