Unless you've got x-ray vision, it can be pretty difficult to verify the quality of work. Is there a proper footing under that wall? Is there gravel under that?

Unless you've got x-ray vision, it can be pretty difficult to verify the quality of work. Is there a proper footing under that wall? Is there gravel under that? Was the mortar mixed to the proper consistency? Is there a second course of brick hidden behind the first one (wait, should there be?) and if so what's the quality of that? That's just what I can think to ask from having had one minor wall built. I'm sure a real bricklayer could do better.