as a rule of thumb if your prone to blisters put it on before you even start day 1. If not have it handy and once you start to feel any rubbing or hot spots put it in those areas to help prevent future blister form occurring. I would also recommend taking it off each night to allow the area to dry out better and reapply it in the morning before you head out. if you don't take it off every night just make sure you air out your feet real good at night. keeping your feet as dry as possible will also help add to the blister prevention process. You might want to keep an extra pair of socks with you to change them out periodically as well. Best of luck out there!