Did you know that in order the average water intake for healthy individuals is 15.5 cups for men and about 11.5 cups for women. The general rule is an ounce of water for every 2 lbs of body weight.
If you are not used to drinking so much water, don't start at this amount. You NEED to build up to that amount and spread it out over the whole day. However stop drinking fluids about 2-3 hours prior to going to bed so that you dont find yourself waking up in the middle of the night having to go to the bathroom.