First, be certain that your boots fit well. Then as others have suggested, try double socks but be certain that does not cut off circulation in your feet. For me, double socks do not help but for others they are great. And as quick as you feel a hot spot on your foot, take off boot and sock and apply Vasoline or something to  the area, or put tape over that area. You should prevent blisters and not need to treat them.