Don't wait to be thirsty before you take a drink. If you are thirsty, you have waited too long. Thirst is actually one of the initial symptoms of dehydration. By the time you are thirsty, about two cups of your body's fluid supply has already been depleted. Although water is not the only fluid, it is the best choice.
Water is absorbed faster than any other beverage and it is calorie-free.
Alcohol and caffeinated beverages should not be counted as part of your fluid intake. These beverages act as diuretics, increasing water lost through urine, and actually increase fluid needs. If you spend time outside you need to consume more fluids. Drink steadily throughout the day, keeping a water bottle or cup at your desk and with you on your commute. Having a water container also acts as a visual reminder.