Double check habit

The trashier the beach site the more important it is to recheck any hole you dig before moving away as you often don’t hear multiple targets under your metal detector search coil.
When two or more metal objects are buried in the same area it is always the strongest signal your metal detector detects, large size metal objects over power small size metal objects, but not always.
A smaller piece of iron like a washer will completely mask a gold ring buried next to it, the reason I always sweep my search coil slowly to aid target recovery speed.
Target recovery speed is the time it takes for your metal detector to respond to a second target after detecting the first target.
Perhaps you get lucky and detect the gold ring before the iron washer sweeping from a direction using a slow metal detecting pace and sweep speed.
Getting back to dug holes during the target recovery process,I make a habit of always rechecking holes and the spoils I dug out of the holes.
Fans of the TV show “ The Curse of Oak Island” may have seen the ending of season five when I recovered a jewel from a broach after rechecking the spoils dug from a hole.
The old broach that came out of the hole was missing its jewel, my habit of rechecking the hole and spoil pile paid off as the jewel was set in a silver frame.
I have found everything from Spanish treasure coins to modern diamond rings checking other beach hunters holes, knowing the object that caused the other beach hunter to dig may not have been the only thing in the hole.
When I search in land I always sweep around the inside of a dug hole using my pin-pointer before filling the hole, especially if the initial target was a good one.
That attention to detail has led to many a good second or third find from the same hole for me. 
Studying how both iron and target masking effect you will help you to winkle out good finds in trashy areas.
If you want a really eye opening experiment, try using a garden rake over a very trashy area you believe you have cleaned out, no doubt you will detect good targets after taking the area. 
Get in the habit of rechecking any hole you dig as one day it will pay off for you.