Hey Rich,
Settings on this machine are pretty simple...
If you want to hunt in disc. mode, I'd set disc at 40 -- the top of the iron range. That way, everything 40 and below (iron) will give a low grunt, and everything 41 and higher (non-ferrous targets) will give you a modulated VCO audio response that has alot of "information" contained in it, once you learn to understand the sounds the machine makes when "seeing" different metal targets. I would run your sensitivity/gain as high as you can, without running into EMI issues (usually can be maxed out at 100). Don't forget to ground balance (which must be done in all-metals mode).
If you want to hunt in all-metals mode, which is a deeper-seeking mode on this machine, I'd run the threshold up to where you just get a hum, ground balance, and go.
These are really simple machines to use, but VERY sensitive and surprisingly deep. If you are using disc. mode, you can run your disc up higher than 40 if you wish, but you will lose some of the iron grunts at the low end -- the higher you run disc, the higher your "zone" of low grunts runs, as well. In other words, if you run disc. up to 60, then your "zone" of low tones will be from roughly 40, up to 60 (shown by the "gray" bars at the top of the screen above the number dial). With this 60 disc. setting, for any target with VDI below 40 (i.e., the iron range), you would hear NOTHING. You can adjust that (the disc. level) to your liking; some folks want to hear ALL the iron, but want it to "grunt" as opposed to VCO audio, so they set the disc. (tone break) at 40 (as I suggested). Others don't want to hear the iron at all, so they set the disc. around 60 (which cuts off the audio below 40 completely). Other times, when guys want to just cherry-pick high-conductivity coins, they may set disc as high as 80 -- thus NO SOUND AT ALL below 80, but all targets 80 VDI and up (most copper pennies, and the dimes, quarters, halves, dollars, etc.) will tone with modulated VCO audio.
Hope this helps,
Steve