Trenchfoot

I suggest riverfox socks, and wearing the issue dress socks under them. The additional layer buffers friction on your foot but adds heat.
Wear your boots snug and ensure they fit properly.
As for soreness, stretch and massage your feet by hand when you get rest opportunities.
In regard to trench foot, expose your feet to sunlight and alternate between pairs of socks and boots when situation allows for it.
Keep your feet dry when possible but to break in the boots when you first get them, take a shower in them and wear them around for a bit. It makes the leather pliable and when it dries it will conform to your foot. The rubber you will have to work by hand.

Get started training now. Walking under load is more difficult than you'd think. If you have access to a gym with variable treadmills use them. Set to about 4mph and select a hill program, wear a backpack. Do it as long as they allow you (some gyms have a time limit. When you're in the field wear a pair of dress socks under your boot socks. The other posters have hit the major points already. Good luck user.