Here are some tips on how to buy an ergonomic chair to spare your back during your long office hours:
One good rule of thumb is to make sure the chair you purchase follows the natural curve of the spine. You want the chair to be somewhat S-shaped but with an outward thrust at the point where your lower back will make contact with the chair. Try out as many chairs as you can. Your quest is over when you find the chair that supports each part of your back: upper, mid, and lower back. As you try each chair, remain relaxed, but don't slouch or lean in any direction. You should be able to feel the chair back mould to your own.
Your feet should be flat on the ground as you sit on the chair. There should be an adjustable lever so you can change the height of the chair according to the height of your workstation. If your workstation is particularly high and you find that your feet dangle from the chair, try putting a footstool or a box under your feet.
Never cross your legs while seated at your workstation. This may be the ladylike way to sit, but crossed legs may lead to chronic back problems. The ideal position is to have your feet together, perpendicular to your knees.
While lots of office chairs claiming to be ergonomic come with arm rests, if they aren't positioned just so, they can worsen the strain on your back, neck, and shoulders. If the chair has arm rests, check that these don't interfere with typing or using your mouse. If you rest your arms on the arm rests as you type, this may lead to carpal tunnel syndrome. The only time you should use arm rests is when you are resting your arms. The adjustable height lever should be used to make sure that when you type, your arms remain bent at the elbow, and parallel to the floor.
A proper ergonomic chair should come with an adjustable back than can both recline and lock into comfortable positions. This should make it possible for you to stretch your back while you are in a sitting position.
In terms of upholstery, you may want to choose fabric for comfort if you live in a hot climate. Still, it's much easier to clean up spills from leather upholstery.