If you've ever spent the day walking in a brand new pair of boots, you've probably learned the hard and painful way that some boots need breaking in. Although hiking boots are generally the worst offenders, even cowboy and dress boots may require some breaking in before regular use. Old boots that haven't been worn for awhile may also require a break-in period. Softening your boots may take up to several weeks, but it's an investment well worth it to achieve a comfortable fit and prevent blisters and skin rubbed raw.
Wear appropriate socks for the boots, and lace up your boots tightly, ensuring the tongue of the boot is straight and centered.
Walk around your house in the boots for short periods of time. You don't want to take the boots outside until you're sure you won't be returning them.
Increase the amount of time you spend in the boots little by little.
Remedy "hot spots" -- where the boot irritates the skin, making it hot -- with hiking sole inserts. These inserts add orthopedic support and help prevent irritation and blisters. You can also soften hot spots by rubbing the area with a rounded object or by applying leather softener.
Take long walks or short hikes to finish breaking in the boots.