The only way to not miss anything is to dig it all. I keep my disc just above the iron range, and I dig it all...even tiny bits of aluminum foil. But, then again, I'm hunting in sites where I am apt to find pewter and tombac buttons. If you're coinshooting and searching for gold jewelry, you'd be safe to keep your disc a little higher (just under nickel), but what about that one dollar gold piece? Or that gold charm or earring? The only way to know what your detector can and can't do is to dig as much as you can. It's why I don't use a meter at all. IMO meters exist just to help tell you when Not to dig...and I've dug great targets that didn't read like anything diggable. I've dug Civil War bullets that whispered at me like an iron nail, and large cents out from under cast iron cooking pot chunks that made them sound like crap. I got a half dime this spring that was deep and on edge and sounded like a piece of buckshot, and a Confederate button that sounded like tin foil that was up against a nail.
Dig it up, or leave it for the next guy. All detectorists are different, but I like to sleep at night, rather than wonder what I missed.
Best Wishes and Happy Hunting,
Buck