Step-by-step: Build a digital maquette
I start by constructing a 3D model of my city. I create basic shapes, and either copy or extrude them into stacked arrays. This gives me skyscraper-like structures with separations for each floor. Then I can twist, bend, stretch and scale each one to give me that futurist look.
I project the 3D rendered image and trace it on to drawing paper. You can also just start painting digitally over the 3D model, but I like having a bit of a line art style to my work. I add destruction and broken windows to the buildings, but much of this will be painted over.
I begin adding colour and value to the piece, using Color Balance adjustment layers to unify the mood if the colours start to get all over the place. I want a sunlit scene, with the light coming in from the back left. Atmospheric perspective is also useful for showing distance and scale.