• Drink one to two cups of fluid at least one hour before the start of exercise.
• Drink eight ounces of fluid 20 to 30 minutes prior to exercising.
• Drink an additional eight ounces of fluid within 30 minutes after exercising
• Drink two cups of fluid for every pound of body weight lost after exercise.
• Both caffeine and alcohol can have a diuretic effect so be sure to compensate for this additional water loss.

Source: The American Council on Exercise, 2001