You can get very expensive chairs, but if you sit on them for lengthy periods of time, you are still going to get aches and pains.
Take regular breaks – at least five minutes every hour – and have standing or walking meetings.
Walk to talk to somebody instead of sending them an email.
If you are working from home, a hard kitchen chair is probably not as good as an office chair, so take more breaks. Relaxing in an armchair or on the sofa will have less of a toll on the body but you will still need to get up frequently. Movement is the key to good muscular-skeletal health.
Understand how your office chair works. To achieve a good posture, it is about being relaxed and having as much surface area of your body in contact with the chair as possible, such as the lumbar support going right into the curve of your back. Start with your feet firmly on the floor or a footrest, and adjust the height. If it is too easy to slip your fingers under your thighs, your seat is too low; if it is too hard, your seat is too high.
Armrests are not meant for you to rest your arms on, they are to help you get in and out of the chair, so don’t worry about them unless you have a shoulder problem. It is inevitable that you will slouch – our muscles get fatigued quite quickly – but if your chair is set up properly, you won’t slouch very far. If you are slouching, go for a walk.