First, I'd get the right topo map and look for streams, creek beds & rivers because they expose rock or have rock beds. Second, I'd inquire about any recent construction or other digging. Obviously, I would also ask the owner where there are rocks laying on the surface. Barring any of those, I might go back to the topo or just look for hills, bluffs, etc.
I'm sure I am looking over something obvious....besides bringing the right tools and asking about where all I could drive or not - logistical stuff to move any rock you find. If what I found was bad stuff...I might look in another area before I spent a lot of time collecting marginal rock.
