A one week fast.. questions??

A few friends of mine and I are going to fast (some of us for different reasons). I personally want to do it for the mind and bosy cleansing. I wouldn't mind losing a couple pounds in the process but that's definitely not my goal of fasting. I need some tips from everyone at MFP as to recommendations for doing this so it won't harm my weight loss, muscle mass (much), or overall health. I have a few questions.

1. I work very hard on Tuesday and Thursday and burn an extra 1500+ plus calories on these days. Would it be better to start the fast Wednesday morning and end it (next) Tuesday evening? Or do you have another recommendation?

2. Obviously I need to consume something over a week, but what? I know some friends who drink lemonade and water while they fast. I was thinking some 0 calorie flavored water with added vitamins. Would it be a good idea to take fish oil and calcium while I fast or no? I want to really cleanse my body so I want to keep as much out of my body as possible.

3. How should I start the fast? Have a normal day of eating or eat like 4,000 calories the day before? And how should I end the fast?

4. How can I avoid gaining weight after the fast when I start eating again?

Thank you all so much!