Use the rule of thirds for your paintings. Your focal point should lie on one of the lines.
Always do a value sketch of your painting before beginning to paint. This sketch can be
as small as a 2x3 although a little larger would be better.
This sketch should contain at least three values. Light, medium, and dark.
When you view this sketch, it should be visually interesting in its shapes not the details.
You should also be able to turn this sketch upside down and have a visually pleasing abstract.
Doing this will ensure a successful painting everytime.