I find the best way is walking in the woods, with no people around. I do that 3-4 times a week for 40-90 minutes. Usually with the dog. It helps to have a long retractable leash attached to my waist, so I don't have to hold it or negotiate every clump of grass she wants to sniff.

I can think through some smaller issues in my office, leaned back in my chair, feet up on my desk. But it's easy to get sucked back into the screen.