I am new as well so maybe my input isn't as worthy but these are the things that go through my head when I find deep target readings.
What is the reading... trash, coin, unknown..
If I know the reading then I have a better understanding of how to approach next. For example, if it's a tin/foil reading, are you somewhere that might typically have foil (near a grill or picnic tables in a park?) Chances are it's probably foil, but if it is then releventchair mentioned something that I do in this case, lift up the coil and scan again. Large objects will appear shallower than they are and tiny objects will appear deeper than they are. I had a case yesterday, a piece of foil smaller than my pinky nail came up as a pull tab 12" deep but it was actually that tiny piece of foil about 2" deep.
Also using the pin point mode (if you have it) to check the size, again as releventchair mentioned, once you hit enough coins you will be able to easily tell if it is a coin sized object.
And another thing I do is, typically, if I get a reading for something say 4" down, I'll go to about 6" and if I haven't found it yet, it's probably a larger (trash) object deeper in the hole.
As I said, I'm new to the game but I do read a lot of articles and watch a lot of videos so it's not only my experience but rather things I have confirmed from research.