Do you have any tips or habits to suggest?
I keep a small wooden chair around for if I'm really too tired to balance. But it's not comfortable either so I don't use it unless I really need to. Wearing slippers seems to be enough, but maybe I'm not noticing/attributing any back pains to it.
Try to distribute your weight evenly to both legs. Don't lean on one leg too much. Try to engage core muscles.
Stand on a mat that has some cushioning.
This is subjective. Eye direction looking straight matches top of the monitor.
Elbow at right angle to keyboard mouse
You could also use an activity to indicate when to stand. For me, I would stand for any online meeting (if back-to-back then I alternate).