A great exercise while being still is to put your attention to various parts of your body: what does the air smell like? What do you hear? How does the chair under your butt and the ground under your feet feel like? Try not to think too much, let the thoughts come and go like cars on a motorway, but observe closely in and around you.

My ADHD brain recoils at the thought of this, which probably means I would benefit even more from doing so.