Estivation
Estivation, sometimes spelled aestivation, is the act of sleeping through the hottest months of the year. It is similar to hibernation, except in this case the purpose is to protect an organism from the hottest months of the year instead of the coldest. Such animals can then take advantage of the coldest, wettest months of the year. Only one mammal does this, a lemur from Madagascar, but reptiles and amphibians all over the world use this adaptation, including desert tortoises and California tiger salamanders.
Cryptobiosis
Some species undergo a process called "cryptobiosis," a Latin word for "hidden life." Animals that use this process hatch out in seasonal rain ponds in the wettest months, mature quickly and lay eggs that can survive total dessication until the next year. Animals that use this strategy include brine shrimp, better known as sea monkeys, as well as Triops and even some fish called killifish.
Water Storage
A camel's hump stores fat, which helps it to survive long periods without food and water. When thirsty, a camel can drink around 50 gallons of water. Once sated, a camel will refuse water if offered, and mostly lives off stored water and moisture in their feed. Similarly, Arizona's Gila monsters, a large, venomous lizard, can store water in the fatty tissue in its tail.
Eating water
Many desert animals obtain quite a bit of moisture from their food. Kangaroo rats have the ability to eat certain cacti thanks to modifications to their digestive tract. This allows them to get moisture from cacti that are inedible to most other mammals, including humans. Other desert mammals make water from dry desert seeds through internal chemical reactions and have modified kidneys to draw as much water from their food as they can.