Draw a large oval or rounded shape for the helmet base
Add a smaller curved line inside the lower front for the opening
Sketch the top dome with smooth rounded curves
Draw the side edges connecting the dome to the opening
Add a chin strap or lower band if needed
Draw a visor or face guard in front if desired
Add vents, seams, or panel lines on the surface
Refine the outline to make the helmet shape smooth
Erase extra sketch lines
Add shading and highlights for depth