It is a good activity that supplements other exercise routines. Walking fills cross-training needs for the fit exerciser and encourages participation for the sedentary, less fit individuals. Because it's easy to build a quality workout around this activity more and more fitness facilities are offering walking programs and classes. Try to find walking surfaces that provide some shock absorption. Dirt, grass, and running trails are good.
Concrete is harder on joints, but fine if there is no pain from the workout.
Asphalt is good, too but gets hot in the summer. Good shoes are the only necessity. The walking shoes you wear should have enough padding in the insoles to protect the foot as it strikes the ground. The heel should be snug and the toe box should be roomy and flexible. There are quite a few brands of walking shoes available and many inexpensive athletic shoes do the job nicely, too.