I can always tell who the military vets are on my survival courses: at the end of the day, they take off their boots, dry their feet, and rub some talcum powder on them. Most of these folks have spent a long time afield over the years and know the value of taking care of their primary locomotion tools.
Prevention is key. For starters, wear quality footwear and socks and take frequent foot-breaks throughout the day when hiking. This means pulling off the boots and socks to let things air out.
At the end of the day in camp, hang socks up to dry. Consider going barefoot, if it’s safe to do so, or change into sandals. Massage some Gold Bond powder or baby powder onto your feet before hitting the sack. All of this self-podiatry will allow your feet to recover during the night, helping to prevent trenchfoot and skin breakdown and preparing your feet for the next day’s hike.
During a long-term survival situation, air out your footwear frequently. Wash or bake your socks in the sunlight every few days, massage your feet each night, and otherwise do your best to keep moisture at bay. The latter is the real culprit in tissue breakdown, so let those feet dry out every chance you get.