The walk step involves first contacting the ground with the heel, then rolling the weight of the body through the foot until finally pushing off with the toes. In a walk stride, one foot is always in contact with the earth, unlike running where there is a split second when you are airborne at each step.
So a shoe for walking needs these qualities:
Cushion - This is very important at the heel, where the most forceful impact occurs and, at the forefoot, where you press off with each step. When you look at the bottom of a typical shoe, there is a dark - usually black - outsole, which is tougher so you don't feel the surface quite so much nor do you wear out the shoe too quickly. Between that outsole and the bottom of the inside of the shoe is another layer. The material of this midsole layer is where the "cush" in "cushion" is derived. A pair of shoes can look great on the bottom and be worn out when the midsole is worn out. Typically this will occur in about 300-500 miles of walking.
Flexibility - The shoe must bend where your foot bends. Since your are earthbound at each step, there is more actual flexion through the bones of the foot. If the shoe is too stiff, you will have foot
Stability - The back of the shoe surrounding the heel should be stiff. Unlike sneakers where you can push in the heel of the shoe easily with your finger, the back of a good walking shoe should be very hard when you push on it. If you can collapse the back, pass on that shoe. If you are walking mostly on uneven trails, look for some ankle support in the design of the shoe.
A good fit - The shoe must be long enough. There should be a thumb's width of space between your longest toe and the end of the shoe. (If a big number makes you nervous, tell everyone your shoes are a size 5! Who's gonna rip off your shoes to check?!). There should be no pressure around your forefoot and there should be wiggle room in the forefoot between the tops of the shoe and your toes. If the shoe is tied properly, there should be no sliding in the shoe.
Air conditioned - Lots of walking shoes have an all leather or synthetic upper. That may make the shoe easy to keep clean, but it will also make for a very hot walk and increase the likelihood of blisters over the long haul. Look for a shoe with some mesh vents. If you live in a rainy or wet climate and you want to try a shoe with a gortex upper, know that gortex is hot and your feet will swelter in the summer. Think about a trading off to a different shoe in warmer, dryer weather.
Try to go to a technical shoe store in your area to be fit if one exists. Always walk around for awhile to see if the shoe feels good to you. If it is uncomfortable in the store, it isn't going to get much better over time. Do not be afraid to try on running shoes. There is much more variety to choose from in most communities. If you happen to live in an area where you have the luxury to try out several different walking shoes and you find one that fits, great, but the shoe has to feel good to your feet!
Socks - You will be happiest in socks that wick moisture away from your foot. Cotton socks will hold moisture and may cause blisters. There are a number of technical fibers available today, such as Coolmax. Look for socks with a high moisture wicking content. These are available everywhere from retail chains like, Target stores, to specialty stores and mail order catalogues. Buy one pair! If you like it, buy more. It will take some experimenting to find out what works best for