Be sure to stay hydrated, like drowning in water kind of hydrated because it helps while being fasted to keep your body functions good and muscles from cramping and stuff like that. Also when you have you meal be sure to have enough protein that your body needs for the day, the other macronutrients tend to work themselves out. Focusing on whole foods and not so much processed foods will give you more nutrients and keep you satiated and better energy levels. I felt weak my first day doing 16/8 and the second day I changed it to 18/6 and have been going at it that way since last Friday. Have enough rest, stay hydrated during the day when you fast, and consume enough protein and adequate calorie intake. Hope some of these tips help out. Im happy that I found intermittent fasting and plan to stick with it.