Ask when you get there? It can be very nice to have a conversation with local person.
The best one I had was on a trip through Washington into Oregon. We pulled off the highway into a little town to pick up some groceries and look for a campground. I asked a guy on the street and chatted for a minute or two about what kind of campsite we liked. Then he said, follow me, and headed down the street in his car. We followed him for something like 20 minutes on backroads and he left us at a fabulous local campground around a meteor crater. Lots of room, good swimming and quiet. I wish I could remember where that place is. I see meteor crater parks on maps of those two states but they look like tourist destinations rather than a quiet local park.