Meditative walking is a very relaxing way to spend half an hour. Some people can just sit there, close their eyes, and shut everything out. I've tried it, and it doesn't work. However, I've figured out how to make meditation work for me. Maybe it'll work for you.
Before You Go
Pick your element. Pretty simple. Are you going to walk during the day, or at night? On the beach, along a trail, or in the suburbs? Pick an area that you think will be most peaceful, and which you can be "in tune" with.
Pick your route. Pick where you'll be walking. Pretty simple. The best route to pick is generally one which will loop on itself, so you don't have to make a conscious decision to turn around and go back.
Learn your route. Learn where it goes left or right. Learn where it goes up or down. Know the route so that you could practically walk it with your eyes closed. (Note that actually closing your eyes while walking can be troublesome, so avoid doing it!)
Avoid crosswalks. Crosswalks mean making a conscious decision to stop and look both ways. It's a better idea to loop around the same path a couple of times than to have to click back into reality. It also means you might walk right into traffic if you're really zoned out. Oops!
When You Go
Don't have plans. Pick a time that you know for sure that you will be free, so that you have the time to do this and not have to worry about being back in time for whatever.
Don't bring your cell phone. It's a ticking time bomb more than anything. Right now, you're the important one, and others can wait. This is your time.
Walk alone. Or, failing that, bring only someone very dear to you, and whom you know will be doing this with you and not start talking.
While You're Out
Quiet your head. Hell, that's the entire point. You're out to meditate, so shut out your thoughts. Stop seeing the pictures of your mind, stop hearing the sounds of your mind. If you have to tell yourself to do so, listen to that voice in your mind and nothing else.
Live through your senses. Experience only the outside world. Look at the world. Maybe you want to look around and see things in ways you haven't before. Maybe you want to just look straight ahead and trance out that way. Listen to the outside. Listen to the wind, the trees, the ambiance. Take deep breaths and just feel the world around you.
Be conscious of your location. You want to pay attention to the world around you...but you also don't want to get lost. Know where you are and where you're going. Stick to the route. You don't want to come out of your meditation and find yourself lost.
Pace yourself. Take your time. If you are walking with someone, you'll also need to be aware of their location.
I think that's it. If you have any questions, comment. If you try this and feel refreshed afterward, comment. If you want to just comment, comment. XD