There are some books and articles available on line and at the library that would help you decide where to start. I have learned so much in reading the posts on this forum as well as the Bowel Cleansing and Water-only fasting boards.
Over the last 15 years I've done:
the lemon juice cleanse,
VE Irons (once without colonics and three times with),
Nature's Secret Ultimate Cleanse (good for week will power), Yerba Prima,
two 3-day carrot juice fasts,
one 3-day apple cider fast,
and the water only.
I have had more deep cleansing with the water-only fast. The first three days to cleanse my bowels I did use psylium and cleansing herbs. But if you are very toxic it can be very debilitating. The total fast was 8 days with about 3 days only on water. (I lost 14 pounds, but gained 5 back after starting food again.) I spent 4 days just lying around. I couldn't move. If I had done more cleansing before starting the water only I think it would have gone better. Also, if you are sensitive to Sugar the lemon juice fast or apple cider fast can work against getting control over appetite.
I am in day 2 of a fast. I drink mostly water and 1/2 cup apple cider am and pm with my liquid minerals and B-complex liquids. I am also going to try just lemon in water. I want to prevent the zombie effect.
Hope you can find what works for you and everything goes well!