When purchasing a VGA cable, consider factors such as cable length, cable quality (e.g., thickness, shielding), connector types (male-to-male, male-to-female), and compatibility with your devices' VGA ports. Choose a cable length that allows for flexible positioning of your computer and display device while avoiding signal degradation over longer distances. Additionally, opt for high-quality cables with gold-plated connectors for better signal transmission and durability.