What do the animals native to the desert do? Or, for that matter the indigenous people? If it is daylight you need to seek shelter from the heat and sun. This means locating a rockshelter or constructing a traditional wickiup from native shrubs. If it is near or after nightfall you face extreme cold. Again, seek shelter and if possible build a fire. Tinder includes any of the dried remains of plants, dried cattle dung, even a few threads of your precious clothing if of natural materials. You will have to create sparks using suitable stones.