I would look at the edge of old lake beds, river banks, and naturally, caves. I suspect that someone with a "trained eye" could find many interesting artifacts. As an example, looking for shark's teeth. Once one has walked the beach where they are, in a week or so, they just pop out at you. I was standing with one between my feet, and I didn't see it. My friend who lived there said, "I was standing on one." The same is true for pottery shards. Once you look for a while, where there are some, you see them everywhere.
This is exactly what happened at either the Meadowcroft or the Topper site (Can't remember which). The discoverer dug down to the Clovis level then stopped. Only after the discovery of the Monte Verde site did he decide (years later) to go back and dig deeper. Below the Clovis level, guess what, he found even earlier human artifacts.