I agree with Flatwater, look for vegetation that is getting or needs a steady water supply to flourish. It is actually easier to find water during a dry spell as the vegetation getting steady water will look better then those in the vicinity. This is how I found a hidden spring on our property.
As a teenager, my grandmother (a fine mountain woman who routinely shot a squirrel for breakfast) showed me to use a long, hard sharp stick to find water. We looked for bushes and trees that looked much better then those around them and then stared pushing a sharpened,long,slim, hardwood stick straight into the ground around these plants/trees. The deeper and easier it is to push the stick down, the closer we were to the water source.
When we bought our wild acreage it did not have a spring (or so we were told). I noticed a line of maples and oaks that were much bigger then those a short distance away. I remembered my Grandma's water lesson and found a stick, got a point on it and started slowly poking my way up close to the base of a huge red oak. I then started working a circle outward from where my stick went in the deepest (over 12 inches) into the soil. I marked the area with rocks so I could find it when we rented the equipment to start excavation on our property.
With a small backhoe, we dug a 3 foot hole under the marked area. Almost immediately the sides of the hole began to get wet and the hole slowly started to fill with water. We hit a wet spring that has yet to dry up.Since then we have dug the hole a bit wider and deeper and plan to use it as an alternative water source. The water flow isn't fast (1 gal. in 6 min.) but over a 24 hour period you have 144 gal. of water. Plenty for us, the garden and animals if we need it. We still don't have a spring according the county...what they don't know won't hurt us! :2thumb: