What are some good tips on ruck marching and ways to prepare for advanced military training?

The key to marches are you feet, IMO. If they are comfy, will you be too. Good, broken in boots are key (i use the wear them in the shower, and wear then dry, althought this doesnt work as well in desert boots). Also, wear black sock liners (dress socks) under your cotten combat socks. This prevents fiction, and makes your feet have an easier time. Although, if its hot, you might sweat a tad more.