According to Lou: Unrelated TidBits

• Before you start painting decide on the concept of your painting.
• Decide on the direction of your light source and have your shadows remain consistent in the painting.
• Paint shapes not objects.
  
• Look for a spot where you can use pthalo blue over green to suggest reflected light.
• Nothing should appear black.
• Three light sources: sun, sky, reflected light off objects.
• Under eaves look for warm reflected light and a cool shadow edge.
• Mixing is subtractive. The more you mix the duller your color.
• In a painting some color should dominate at least 50% to 66% of the paper.
• Neutralize a color by using Burnt Umber (not Winsor Newton) or the color's complement.
• Warm colors advance and cool colors recede.
• Generally the sky is a light value, while the ground plan is a middle value.
• Your best color and contrast should be at the focal point of the painting.
• Dark value surrounded by light value advances.
• 5-Value system: light, mid-light, middle, mid-dark, dark.
• 9-Value System: white, light-light, light, mid-light, middle, mid-dark, dark, dark-dark, black.
• Transparent paints and opaque paints don't mix well.
• Do not use two intense complements together, one should be duller.
• Earth colors bleed.
• Chroma advances.
• Color is about value and light.
  
• PAINT! PAINT! PAINT!