Some decent options in this thread, I thought I'd add some general advice, which I could have used in the past.
Firstly, figure out if you want / need a neck rest. This turns out to be important for me, and I would not want a chair that doesn't have one (this point could be expanded with exceptions).
Next, adjustability is key. Some things are standard (backrest angle, height), but many are rarer. For me, being able to adjust the height of the armrest was eye-opening. Without this, you will either slouch in the chair, or hold your elbows in the air, neither of which are ideal.
Lastly, a word about sturdiness and durability. Some chairs start to misbehave as they age, e.g. I once had a cheap office chair which started to "list" slightly. I didn't pay much attention until I noticed frequent cramps on one side of my back, and realised it's because I'm sitting at a few degrees angle to the right.
Overall my advice would be: get the right chair (for you), sit correctly in it, and do plenty of exercise. The best chair in the world doesn't help enough if you sit for 14 hours every day, without any of the latter.