The idea, if you refer to physical walking as a form of meditation, is to see it as a set of processes. Most people, if they slow down their walking drastically and really pay attention to it, will find that they have difficulty in not falling over. Attention is placed on the different steps. Lifting the foot, moving it, and setting it down. Speeding up the steps, this can be shortened to left, right, left, right. Slowing it down, the different parts of the feet can get attention as they lift from the floor and go back down. A path long enough to take several steps in one direction and back again is needed. At some point it will begin to affect regular walking used to go from place to place. Walking meditation is good to alternate with periods of seated meditation. The seated meditation increases concentration while the walking meditation counters and growing dullness of mind.