Begin with fit. Your feet should rest comfortably, and the seat should support your thighs without pressing sharply behind the knees. A chair's height range must work with your desk, while its seat depth and width should suit your body. If several people use the same workstation, adjustability becomes especially valuable. Measure the available floor area too, including the space needed for the chair to move and recline.
Look for adjustments you can understand and use. Seat height is essential, and a changeable back angle or lumbar support may help you fine-tune the fit. Armrests can be useful if they allow your shoulders to relax, but poorly positioned ones may prevent the chair from sliding under the desk. Upholstery affects breathability, cleaning, and wear. A padded seat is not automatically comfortable for long periods if its shape does not suit you.
Check assembly instructions, weight limits, warranty terms, and the condition of components that experience regular movement. If possible, try sitting in the chair for more than a brief moment and test each adjustment. No chair can compensate for remaining still all day, so consider whether you can change position and take breaks. A good choice is a chair that fits your setup and supports comfortable movement, not one defined by a single ergonomic label.