This is day 1 for me too. There are a couple of us fasting together. We are over at the Water Fasting forum. If anyone wants to join us (Diggy is already there!) you are more than welcome.
Anyway, I am doing much better than I thought I would. No headache and lots of energy. I am drinking A LOT of water, hoping that if I can keep myself hydrated I can either totally prevent a headache or not have one as bad as I would otherwise.