Key criteria include loft (height), cervical support geometry, firmness, and compatibility with your sleep position. Side sleepers generally need a loft that matches shoulder width, while back sleepers need a lower design that supports the neck gap. Consider material trade-offs such as heat retention (memory foam) versus breathability (latex), as well as washable covers and allergy sensitivity. Shape retention matters—pillows that compress quickly can compromise alignment. If possible, choose options with a trial/return policy to find the right fit. If you have a cervical disc problem, advanced spine issues, or neurological symptoms, selection is safer with professional guidance rather than a trending product.