I hunt mainly jewelry. I have for quite some time now. I see people all the time post that to find rings, you've got to dig that trash. I have been saying for a long time, but, you can increase the odds of finding rings and not dig all the trash. Notching out the known stuff, like tabs, is simple enough, but for me, I notch, often just in my head, each site. If you find 3-4 pieces of aluminum at VDI 18-20, then don't dig those, but a 17 is worth a looksee. It isn't about knowing what VDIs you know what they most likely are, but the ones that you don't see often.
Size. Once I have a VDI of interest, I switch to pinpoint a good 6" above the ground and go over the target to get the size and shape. if It is pinpointed as small and the same from all sides, and an out-of-the-ordinary VDI, it is worth a dig.
And this is where not all detectors are good for. XP Deus & ML Equinox 800. Very good at pinpoint sizing and shape.