I claim that rock pile sites are most likely either on a hill shoulder looking out over water or at the headwaters of a brook - where a spring or break-out zone produces water coming out the side of a hill. To prove this point, in the past, I proposed the following experiment:
1. Take a fragment of topo map, of someplace remote and not yet explored. [This is how I came to choose Leominster State Forest.]
2. Circle a number of likely places on the topo map.
3. Go to those places and locate rock piles.
It turns out this is a flawed experiment. First, it turned out to be impossible to get to most of the locations I had circled - because of mountain laurel. Second it was hubris to think I could guess the conditions on the ground or the type of rock pile sites to be found at this "remote" location. Also, you need some rule about how big to make the circles and about how thoroughly to cover the available map area with circles.
So what was the result? When I first tried it, I was only able to get to two of the circles - with no rock piles in either. Each time I tried to get to one of the other circles, I had to give up but ended up finding rock piles in places I should have circled.
Knowing this, how can we improve the steps of the experiment? Well, be more systematic about circling all the likely places and pay more attention to accessibility. (Ironically, last weekend I did get to a third circle - the one second from the top right, and I did find rock piles there.) I tried to follow the modified guidelines a few weeks after the first experiment - I made a largish circle around the area near Redemption Rock (just south of Leominster State Forest), and ended up finding a number of rock pile clusters. In the end, I do not think the experiment is too successful. It is hard to be sure it evaluates site prediction when it could just be that there are lots of sites and you stumble into them regardless of what prediction/search strategy you are using. However the experiment does have one clear beneficit - it gets you looking at the topo map and gets you out exploring new territory. It does result in locating new sites.