Walking meditation is a bridge between formal sitting meditation and informal meditation in everyday activities. It is also useful if you want to meditate for long periods continuously. Alternating sitting and walking provides a way to relieve the stress on your body without ever leaving meditation entirely. Walking also serves as an antidote to both the tiredness and restlessness that can obstruct meditation.
Walking meditation is easiest in a quiet place without distractions or obstacles. An empty room large enough to walk in circles is suitable. Even better is an unobstructed natural setting, such as a park. Walking meditation is valuable but more difficult in an urban setting.
Walk with your eyes looking downwards at about 45 degrees, but keep the head upright. Allow your gaze to move smoothly over the ground, rather than jumping from one point to the next. This is much easier if you allow your eyes to relax and defocus, so that your vision is slightly blurred.
Be aware of each part of your foot as it presses the ground in succession. Be aware of sensations: of your trousers brushing your legs, of the rhythmic contractions of leg muscles, of the slight brush of air against your skin. This is easier if you walk at about half the normal speed.
When you find that you are distracted by thinking, return to find the presence of awareness in sensations.
Pay no particular attention to the objects around you, but be aware of your body moving through space. As a variation, feel that you are motionless and that space is gliding past you.
Try this for fifteen minutes. That is enough to get the flavor. With experience, you can engage in walking meditation for periods of seconds to hours, and any time you need to walk.