Dehydration would be your Number 1 enemy. If you are able to offset dehydration you would are almost ensured of survival. Well, you could also starve to death, but we'll talk about that later. Dehydration is a nasty little menace because many of your body's most sacred resources require water to function properly. A properly hydrated body can cool itself through sweat - and it also will perform better in stressful situations, such as, oh I dunno, being stranded in the desert for an extended period of time.
Dehydration has many forms.
Low-level dehydration is common even among most people today who fail to drink enough water on a regular basis. Symptoms may include dry mouth and excessive thirst. Take a peek at your urine - a dark yellow colour indicates insufficient hydration, while a pale, happy yellow will tell you that you're on the right track. Critical Dehydration generally occurs in hot, arid temperatures, and is often the result of an emergency or survival situation such as a downed plane or any other sort of mishap that might be terrifically inconvenient and scary. Dehydration at a critical level is progressive and is indicated by dizziness, heat cramps, and a weak, faint pulse.