Really only two things.
1# be in ketosis before you start.
2# take a couple shots of water with a teaspoon of baking soda the day before you start fasting. Baking soda helps the kidneys adjust to the fast and will prevent kidney stones and other issues form arising.
Other than that it’s only willpower that gets you through it.
Binged so much food for a week. Chips, like 8 different sort of chocolates, ice cream, pizza, alcohol beverages, baked yummys, a lot of bread etc - ketosis ruined :D
Now went instantly back to DFing and feels good man.