I'm doing The Master Cleanse for 10 days, which is the minimum suggested time in the book. If you haven't checked out the book yet, I would advise you to.
For me, when doing the cleanse, weight is always an issue. I'm on the side of afraid that I'll loose too much or will do some damage.
Some of it comes down to faith, Mr. Burroughs in the book says that if you are underweight, you won't loose anything that you don't need. In other words, the only weight you loose is what your body doesn't need anyway.
But I track my weight while on the fast. Right now I'm on day 5 and have lost 2 pounds. Which seems pretty remarkable to me, since that 2 pounds is mostly food that's in my instestine when I started.
I've done the Master-Cleanse about 5 times now, and I even though I stay away from dairy for the most part, after doing the Master-Cleanse I can have some dairy and I don't get gas or bloating right away. A little dairy is okay, which before it seemed that a little dairy would upset me easily.
The first 2 days on the Master-Cleanse are the hardest, after that it becomes much easier. When I say hardest, I mean, I have very low energy on those days so I plan a time when I can rest while on the fast. After the 3rd day my body becomes much more used to it.
The real cleaning of the fast doesn't seem to start until day 5 and after. This is just based on how I feel and how I percieve my body to be doing.
I've also noticed that every time I do the MC, it is easier. I think it is a process that my body is learning about.
When doing the MC, the flushing part is the most important! Don't skip on the laxative tea or the Salt Water Flush! And the Salt Water Flush takes some experimentation to see how your body reacts to it. Some days are better than others for me and I'm trying to figure out why.
I've never done the liver flush, but am curious to see what it reveals.
The only other advice I have is, outside of the MC, eat a healthy diet. This is something that I'm not always good at doing. I've eaten my share of hamburgers. There was a post on this website that said, it's much easier to Master Cleanse or Liver Flush than to eat a healthy diet. I think that is a wise saying.