I've recently done a 22-day juice fast with the intention to clear my body of old stuff accumulated over years and decades of improper eating, and to simply give it a time to rest from digestion. The most challenging thing about the fast is a mental aspect - even though some detox symptoms are to be expected, the real struggle is to overcome the tricks and cravings of the mind. Here are some things that I found helpful along the way.
Take notes of everything. For each day make sure to write down what you drink, how much you drink, how many bowel movements you've had, how you've felt and what challenges you've faced. This will make it easier to find patterns, perhaps even predict things based on previous experiences, to make sure you're drinking enough etc. Also, with no digestion you might find that you're having more creative ideas, downloads and inspirational thoughts. Make sure they don't go to waste.
Watch inspiration stuff / don't watch recipe/food videos. Don't make this mistake, especially if you are new to fasting. Watching food videos is a recipe for disaster in the beginning, while you still haven't mastered transcending the cravings. Instead you can read or watch videos who've gone through the juice fasting experience so they can provide additional inspiration. I can point you to few of them if you need it.
Engage in light, bodyweight exercise, jogging or walking. It's important to stay active during the fast, to keep the lymphatic system moving. Stagnant lymph system won't have the strength to get the toxins out. Heavy training is possible but I wouldn't suggest it, it's best to stick to simple and effective exercises and activities and rest when your body calls for it.
Introspect, relax, make this the best experience you can have. During the fast all the senses magnify, smell, sight, taste, touch - you will be faced with feelings as intense as never before. Give yourself permission to enjoy this experience and don't run away from old, repressed emotions coming to the surface, if it happens.
Juice enough greens and vegetables. Green juices (and citruses) are more astringent and will pull toxins and plaque from bowel walls, fruit juices are good for washing it down and also keeping you satiated with enough calories. Make sure to incorporate both keeping in mind that the main goal is to remove as much waste as possible.
Stimulate bowel movements. Like I said, it all comes down to this. You don't want juices to release toxins back in the circulation and then not have it removed from the body. So, stimulate the stomach with massage, exercise and move the lymph, and using enemas is another useful practice.
Buy local, seasonal produce. Buy produce that yields a lot of juice like watermelons, cucumbers. Make sure to always have enough fruits and veggies to choose from so you're not tempted to abandon the challenge. Drink enough juice which is at least 4-5 liters. Water is not necessary to be consumed during this period. Create a juicing schedule that works best for you. I personally preferred making all my juices in the morning so I have the rest of the day free.
Spend time in nature if possible. You might be very sensitive during this time so you may want to intuitively spend time in nature and even alone. This is a time for yourself, to get your mindset right. Be in the sun, walk barefoot, feel the connection with nature and everything around you. Juice fast is a great reset to your true self.
Let me know if you think about trying this!