At the beautiful Pacific coast of Oregon there are many, many state-owned waysides and access points to our beaches. Predictably, the beach area within 1/4 mile of the parking lot always has the crowds. The further you walk, the fewer the people. This predictor tends to work well almost everywhere, in my experience.

Another rule of thumb I apply consistently is "if you want solitude, don't camp near a lake". People are drawn to lakes for many reasons: swimming, fishing, the guarantee of a view across the water, and they are just so easy to see on the map.