The best way to prepare your body for a Liver Flush is by changing your nutrition to raw food. Since raw is generally hard on the body you will need to blend everything. Do some research on green smoothies. They are not only super delicious but they provide you with the electrolytes, vitamins and minerals you need to rebuild you adrenals. People report feeling more energetic within a few days of drinking the smoothies. You will not feel hungry at all.
Once you have built up enough energy, you will be in a position to do liver flushes. The body cannot release toxins without enough energy reserves.
Look up http://www.rawfamily.com
for recipes and inspiration.