How do I sit properly?
The best tip for sitting properly is to sit in a straight back chair as little as possible. If possible, never.
A straight backed chair positions the spine in a manner it was not built to assume, unless for a short period of time.
There are many ways to sit that won’t damage your spine so quickly.
Primates have 30 millions of years history of sitting without chairs. Is it reasonable to think our backbones changed to accommodate a 6 thousand year old cultural artifact?
Sit as close to the ground as possible, whenever possible, for the sake of your spine, knees, hips, everything. Get some cushions. Lower your tables.
Recline whenever possible and keep the weight off your spine. There are many ways to recline or sit. Sometimes the line is blurred as to what exactly is sitting and what exactly is lying down.
If eating sit low to the floor. It can take some considerable time to get used to it. Get some cushions and work your way down. Start out slow sitting at the computer or watching television for an hour a day for a few days, weeks…, whatever, to start.
In conclusion: sit in straight backed chairs as little as possible. Recognize the body is not built to hold the straight backed chair position for extended periods.
Sit down close to the ground whenever possible to stretch and balance the back muscles. And especially after a long period of sitting up straight in a straight backed chair. Lotus as shown below is a balanced position that can be maintained indefinitely.
Balance is everything.