Finding a subject you like is only half the battle. How are you going to arrange it on the page? It's easy to do a camera-eye view--been there, done that--although sometimes that may be the best way to represent your subject. First, decide what you want to express about the subject and then select a point-of-view that suggests this meaning. In my windmill sketches, the top sketch makes the subject small in relation to the sky, suggesting abandonment and loneliness. The sketch at the far left zooms in to show a windmill among desert rocks, broken-down and useless. The close-up at the right is a more design-oriented treatment, using the shapes of the vanes and the negative spaces between as a visual interest, rather than emotional appeal. With the point-of-view established, you then use color and value to complete your statement. Choose a subject you like and make three sketches from different points-of-view--then create a painting from one of your sketches.
More on design: The New Creative Artist pp. 78-100. See also p. 117 for more on the windmill sketches.