Set your pen or pencil to a loose, light stroke. Do not worry about clean lines. Sketch 5 to 10 tiny, abstract shapes (thumbnails) focusing purely on the silhouette.

Ground your design in recognizable, real-world mechanics, anatomy, or architecture. If you are drawing a starfighter, it should still have recognizable aerodynamic shapes, thrusters, or a cockpit.

In science fiction, you cannot rely entirely on direct life reference. You cannot step outside to photograph a cyberpunk megacity, a deep-space dreadnought, or a biological alien mech. You must invent them.