These are keys to paint successfully in any medium and no matter what subject you want to paint.  These are a good set of rules to go by when you want to have a successful painting.

      1.  One center of interest in a painting
      2.  Perspective
      3.  Prevent the viewer's eye from leaving the picture
      4.  Guide the viewer's eye into the painting with directional lines
      5.  When in doubt simplify your design
      6.  Simplify areas to accentuate detail
      7.  Choose the best lighting for the subject
      8.  Relay lights against darks, color against color
      9.  Group lights and darks to avoid a spotty painting
    10.  Make the focal point a tonal climax
    11.  Use the decorative cast shadows of trees
    12.  Make shadow directions consistent
    13.  Paint luminous shadows
    14.  Paint the foreground in shadow, for dramatic lighting
    15.  Create atmospheric distance by use of color
    16.  Paint cool shadows to make sunshine sparkle
    17.  Place  horizon line above or below the middle of the picture
    18.  Make sizes smaller in background to create depth
    19.  Create depth by strengthening foreground detail
    20.  Make tree shapes varied and interesting
    21.  Keep sky lighter on the side of source of light
    22.  Vary cloud shapes for better design