I'll start with one below. Hopefully we can build a collection of actionable tips that we could start doing TODAY. So, no theoretical discussions e.g. whether going for a walk is a good thing. Also, please provide a reason for your tip.
So, here's mine that I've started doing
At the end of the working hours - Pack your laptop in your backpack. Don't just close the lid. Unplug any dongle, cable, everything. Next morning setup everything for your work. This way you'll prevent yourself from that urge known as "just check this tiny little thing that will eat 2 more hours of my free time". No matter if you are at the same desk in your home for every day, just start doing this. If it seems like too much remember that in pre-corona times you were doing the same things. Plus commuting.
Reason for this tip is that in consecutive wfh you may lose the sense when are you working and when you're not. So you can switch to a 16h+ working hours which is not good. You'll burn out. You're also "stealing" time from your family (if you live with someone).
Who's sharing their advice next?