you should have your sens to as high as possible without getting a lot of feedback
from your machine, or rather lower your senz to the point where you don't get
"hunters chatter" small pops and clicks associated with a high level of senz. Some sites you can set
it higher, some sites you have to set it lower. to make your machine stable. Tesoros are famous
for this chatter at hi senz levels....
As for discrim levels, well if you have a basic no meter machine and you set it just above Iron,
then in a football field, or school yard you will dig everything, this includes but is not limited to
things like foil wrappers, pencil erasers (horror) scraps of aluminum cans, pull tabs, pull rings without
the tabs, pull tab ends without the rings... and then if your really lucky after about 100 of these
signals you might (only might) get yourself a gold ring...
by my calculations you have to dig about 100 "other" targets before you get a nice ring...
and that does include pocket change...
my two cents worth..