A good way to prepare for a UT fast is to cleanse the colon first and make sure you have at least 2 or 3 BMs daily. One BM daily or less is not enough to cleanse well. You need to get and keep things moving.
One way to do this is by using IF1 daily.
The liver herbs Desmodium and Phyllanthus Niruri are also herbal laxatives that help speed things up.
You could also take Magnesium Oxide if you prefer.
You could do one day a week juice fasts for a month or two, and then try a UT fast.
Juice fasts while taking in a lot of UT might be a better idea for some of us, I'm not sure, but I plan to work on it.