Marian Haddad pointed me to a marvelous article, "Solvitur Ambulando," by Carol Keeley on Ploughshares on this topic.
I walk every day, often in the evening or at night, and sometimes twice a day, midday and evening. I walk when I feel anxious, tense, expansive, in need of a break, bored, even tired. I walk in the morning often to glean natural images, not necessarily to write about but just to wonder at. I think sometimes poets are the last people on earth to cherish a sense of wonder and make it their job to do so.
Walking always brings me at least one wonder, whether it's something as predictable as a star or moonrise, or a surprising scene in the street, or a wonderful smile from a complete stranger than alters the way I feel about the world.
I'm happy to learn from this article the long, long list of writers and philosophers who made daily walks part of their meditative practice. I think in the East they sit in caves. In the restless West, many of us walk.