Through a visualizing technique: I listen carefully to the client's ideas and desires and I listen for the things he or she is not telling me. What they want is usually in between.

Then I lie down, close my eyes and do absolutely nothing. In a few minutes, hours, days... a week (it depends on the complexity of the commission), I will have the entire painting visualized in my mind, every detail, exactly as it will look when it's finished.

The rest is easy: I do the required research, gather the necessary props and materials, make some mental revisions, and then, I paint the picture that's inside my head.