I'd start by detecting an area outside the foundation/cellar hole to make a spot for surface debris. Then detect/rake/detect my way inside....even digging inside if you keep finding stuff the deeper you go. Once the inside is TOTALLLY detected, start working on the outside, expanding my way from the center. Try to find other related places close by, such as a well, shed/outbuilding, outhouse, barn, etc. Hit those new spots too, and the paths between them.