How should a bicycle helmet fit to ensure optimal safety and protection while riding?

A bicycle helmet should fit snugly on the head, with the front edge sitting about one to two finger-widths above the eyebrows. The straps should form a V-shape under the ears and be adjusted so that they are snug but not too tight. The helmet should not move around when you shake your head. This proper fit ensures that the helmet can effectively protect your head in case of a fall or collision while riding.