find something to occupy your time with, boredom is my #1 killer in long term fasting. keep up with hydrating and electrolytes. once you get past the 3 day hump it should be smooth sailing depending on how long you plan to go.
Get used to eating wholesome food and aim lower on carbs, this will get your body used to opening your fat stores more and remove the reliance on sugar, this will help go longer - not required but def helps