Hi Merlin,
Hope you enjoy the F5.
I gave this advice to a person who was brand new to metal detecting.
Set the unit in DIsc mode, d4 (4 tone mode), Gain on 80, Theshold on -9, and Max out your Discrimination. Only recover repeatable high tones. All you'll be hunting is silver and copper and clad dimes/quarters/ etc. Just get use to doing that for awhile. Then when you are comfortable with both the digging and high tone targets, notch in the Nickel range and hunt that way for awhile until you learn that range of targets. Then as you feel comfortable, add in another segment, like the zinc segment. It has has a different tone and you'll be looking at a completely new range of targets.
It wont take long to learn whats good and whats bad, your recovery method will improve and you'll grow more comfortable with the unit. Then you can raise the threshold setting up to 0 and spend time on the deeper and smaller targets.
Most of all, don't be afraid to limit your audio input with the disc and/or notch settings. Keep the audio feed to your ears understandable. When the trash gets too heavy, raise your disc or notch it out so that you can still hunt the good stuff.
Maybe a few guys will post a picture of their trash next time out so you won't feel so bad about your trash ratio. As a gold jewelry hunter I dig quite a bit of alum trash. Foil and tabs, canslaw, and ring pull tails.
Hope that helps.
Mike