The material of your office chair will make a big difference in comfort. Leather and vinyl are easier to clean, but fabric or mesh breathe easier. The rest of your chair may be manufactured from both metals and plastics. You should look for the chair to have five 'spokes', which are found at the base of the chair. Most standard office chairs come stock with wheels for easy maneuverability at your desk.
Especially if multiple people will be using your office chair, you should make sure that all elements of the chair are adjustable. This includes the armrests, seat and back supports. A chair without adjustments is not ergonomic, so look for chairs that have multiple adjustment options to ensure constant comfort.
A good office chair should support your spine from top to bottom. Lower back pain, especially, is a common complaint among office workers without proper seating. Your lower back should fit comfortably against the lower lumbar support of the chair, allowing oxygen to your muscles and blood flow to the brain. You'll be amazed at the energy you have with the proper back support.