Well... Of the top of my head: use a proper keyboard, use all of your 10 fingers, code in a proper body position. Hands should be in a natural position most of the time.

Standard laptop keyboards and mice are a crime against one's hands, it's generally better to replace 'em with something ergonomic.

I did boxing as a university sport. That was the worst choice possible: I developed early-stage osteoarthritis.

Tendon stretches a couple times a day [0] Whenever I start feeling pain in my hands/wrists, it's because I've been slacking on doing these stretches.

[0] https://www.youtube.com/watch?v=cD8BGa3p1Ms

1. keyboard

2. Posture/ergonomics

3. Take frequent breaks while coding.

4. do minimal typing when you are not actively coding.