Write down your feelings, how hungry you are, how you are feeling spiritually, how your prayer has been. Stay away from it as much as possible during the first 3 days. Get plenty of rest. You may tire easily the first few days. Contrary to popular belief, you can work and fast.
Activity actually tends to suppress hunger.
There are men in our church who have finished 7 day fasts while holding strenuous jobs. Light exercise and walking will do much to invigorate you. Drink at least 6 glasses of water a day. Your body has an automatic tendency to reduce the amount of water it releases if it does not receive an adequate supply of fresh water. Often times headaches and hunger are relieved by drinking water.