In the situation one is stranded in the desert, there are two essentials to surviving: finding shelter away from the sun and staying hydrated. There are a few sources of water in the desert, which are listed in this article.
Foremost, if you have bottled water with you, you should not ration it. Instead, drink it all at once — people have been found dead with water remaining in their bottle. Assuming there are no bodies of freshwater around (such as a river), plants, the air, and animals are the only source of water. Some plants, especially some species of cactus, contain water in a form that can be tapped and drunk directly. More often, however, the moisture in a plant cannot be obtained by any method other than the use of a still, which can retrieve water from the air.
Water can be added to the surrounding air by placing plant parts in the still (but outside the area for capturing the pure water). A simple still can be constructed of plastic sheeting, some rocks, and a cup. Simply dig a hole deep enough to hold the cup, with a couple of inches to spare. The wider the still, the better, since it will have more surface area for water to condense on. Place the cup in the center of the hole and cover the hole with plastic (clear plastic is better than opaque, since it absorbs less heat). Use rocks to secure the edges of the plastic and place a small rock in the center of the plastic sheet to pull it down so that water condensing on the plastic drips into the cup. Such a still does not produce enough water for a person to live on indefinitely, but even a little bit of water can improve one's chances of survival.
If there is no available liquid and you are severely dehydrated, drinking urine can become an extreme survival option.
Any activity or situation that promotes heavy sweating can lead to water intoxication when water is consumed to replace lost fluids. Persons working in extreme heat and/or humidity for long periods must take care to drink and eat in ways that help to maintain electrolyte balance. Even people who are resting quietly in extreme heat or humidity may run the risk of water intoxication if they drink large amounts of water over short periods for rehydration.
What not to drinkEdit
Drinking alcoholic beverages will slake your thirst temporarily, but due in part to the diuretic nature of alcohol, will leave you more dehydrated than before. Since alcohol is a poison, the liver aggressively removes it, and a lot of water in the process. Alcohol and water bond covalently, and boiling alcoholic drinks will not remove the alcohol any faster than it will remove the water. Drinking saltwater will lead to water being drained from the body, because of osmosis.
(source: deleted Wikipedia article Water in the desert