The ability to paint or draw is important but the essentials to creating a successful work include originality, knowledge of color, texture and individuality, and eye movement through the painting.
Creating something original and unique can be next to impossible, but we can learn by looking and studying what has been done. To make an interesting eye catching composition, proportions have to be considered including never equal amounts of anything: color, darks and lights, or division of space. Find the best use of values and relationships of color and textures. I have found that sometimes just a stroke of the brush will bring a new idea or dimension to a painting in progress.
Before I say a work is finished, I ask the following questions: Is there a contrast of lights and darks? Have I varied the size of shapes? Is one color dominant? Are the textures interesting? Are the proportions interesting? How much realism should I employ and have I expressed what I wanted?
I don’t always heed my own rules but I try to lose myself in the work and enjoy the challenge.