Blisters are mainly caused by friction, heat and sweating. Lubricating the skin can reduce friction and prevent blisters. Applying lubricants (like petroleum jelly or body glide) before putting on socks helps to reduce friction.
Minimizing moisture on the feet by using drying agents is another way to reduce blister formation. Apply foot powder or cornstarch to your feet before putting on socks. This helps the sock to glide over the foot a little more and prevent blisters.
Choose socks made from synthetic, soft wicking fabric such as coolmax (NO cotton - cotton can cause blisters on your feet). Carry a spare pair of socks. Change during your walk if your feet become sweaty or wet.
Your shoes must fit properly to avoid blisters. Too snug or too loose is always a problem. Ensure that there is 1/2 inch space between your longest toe and the end of your shoe. Be sure that you have enough room to wiggle your toes inside the toe box and that your heel does not slip when you walk. Choose shoes that breathe well and inspect the inside of your shoes for seams or worn areas that might produce extra friction.
Stretching will add flexibility and can make your walking more comfortable. Warm up for five minutes at an easy walking pace before stretching. Never stretch cold muscles or you risk tearing them. Find an upright pole, fence, or wall that will support you for leaning into some stretches.
Select snug-fitting (but not tight) clothing. Clothes that are too tight or too loose can create friction and chafing. Do not wear untested or unwashed new clothing. Wear a hat and bring a sweater and/or nylon windbreaker with you in case of cool temperatures.
Most importantly, wear comfortable shoes for walking and a synthetic pair of socks (no cotton). Some people choose to wear two layers of socks (or a sock that is made with double layers) to aid in blister prevention.
Wearing a waistpack to carry water and personal items, like money and keys, will make your walk more enjoyable. Items like a camera, sunblock, lip balm, extra socks, pain reliever and antiblister aids are helpful to bring with you.