"Woops! I meant to write fisting. My bad!"
--LOL! Nice one! (Ya know, you may wanna try that cleanse before before your fisting.)
But seriously, there are a lot of different types of fasts for different purposes; the subject is as complex as you wanna make it, so I recommend getting the advice of a good herbalist beforehand. Info on the lemon juice cleanse online usually comes with good generic info on fasting, which is handy considering that:
"There are 90 books on fasting in print [in America], most all of which are mutually antagonistic and will hopelessly confuse any intelligent cybernaut. The only thing they all hold in common is their recommendation that one should never do a prolonged fast without skilled, veteran, professional supervision, initially. Quite simply, one without experiential knowledge and distilled wisdom in our field can't be expected to know how to deal with all that can arise (physiologically, psychologically and spiritually) throughout a prolonged fast." www.fasting.com/start.html
You've already got some good tips already, but I just wanted to add that you are wanting a general cellular detox, then remember to stay really well hydrated, or you'll be wasting your time. Taking mild, blood-purifying, liver-detoxifying herbal blends in addition to your fast can be really helpful, but again, see a good herbalist or naturopath first.