The cleanses before a fast are beneficial to clean out the toxins, so you can do kidney cleanse, Colon Cleanse
then liver flush.
Eat raw foods or juicing
with fresh fruits and vegetables, at least a week before the fast, if not for two weeks.
Fasting benefits you even if you fast for a day. Expect to lose 1lb per day. Also take one day at a time and when you feel that you can no longer fast then stop and refeed.
I am bit confused about your intention since you posted in Fasting:Dry forum and not Fasting: water only forum. If you intend to do dry fast I would not recommend more than 3 days.
During the fast drink distilled wate or filtered water as per thirst, rest a lot and keep warm. Do not consume anything but water that includes cleaning teeth with toothpaste or using mouth wash, taking vitamins or any other supplements and teas.