As I do with every painting I do, I block out the colors and lighting first like this, before I start painting. This is how it looked at first! Color blocking like helps establish the mood, light sources, and focal point, while giving me a color palette to work with once I actually start making brush strokes.
The elements of the painting were separated into three groups. The character and objects in front of him, the foreground (bar/counter area), and the background (everything behind these two groups).