Obviously, you would go to see a foot doctor if you sprain your ankle or develop debilitating tendinitis. However, there are a lot of seemingly small foot problems that patients often ignore, but that actually deserve treatment. If you're dealing with any of these issues, then it's a good idea to make an appointment with the foot doctor.
Do one or more of your toenails seem to be growing into the skin alongside your nail? Maybe you pick the nail out from under the skin now and then, or maybe you try to trim it in a special way to avoid pain. Ingrown nails may not cause any pain or big issues initially, but they can get worse quickly if not trimmed in just the right way. If you see a foot doctor, they can show you exactly how to trim the nails to prevent them from worsening or leading to an infection. It's better to do this now, when things are going well, than in five years when ingrown nails make it painful to walk!
Cracked skin on your feet may be embarrassing and ugly, but that should be the least of your worries. It is really easy for the cracks to become infected, either with bacteria or with a fungus like the ones that cause athlete's foot. A foot doctor can help you devise a strategy to soften your skin and heal the cracks. They may recommend a specific cream for you to apply, or they may even file down some calluses that are making your skin overly dry and prone to cracking.
When you get out of bed in the morning, do your arches feel tight? If the tightness wears off after you take a few steps, it's easy to ignore. However, this is usually an early symptom of plantar fasciitis, which can become downright debilitating if you don't take care of it early. See a foot doctor. They can make or recommend some orthotic inserts or foot wraps to ease the strain on your plantar fascia during the day. This will encourage these tissues to heal rather than become more painful over time.
It's often best to see a foot doctor at the first sign of problems, even if they seem insignificant at the time. Foot problems tend to get worse, not better, without the right care, and you can rely on a foot doctor to provide that care.