Dry river beds may hold water under the ground. The best place to look is on the outside of the bends, deep hollows and shaded sections. If you find damp ground you can dig a hole and it will soon fill with water.
On beaches, dig above the high tide mark. The sand filters out the salt and the hole will fill with fresh water.
Where green plants are no higher than 2m high, you can try digging around root systems, again collecting the water in holes.