Welcome!! Great advice has been posted by Chase and other members. Research, location, and of course having access to un-hunted grounds, are all key to finding silver, and everything else. MD'ing 101
Having stated that, I have just purchased a 800 and will soon return to sites that i believe were untouched before i began detecting on them years ago. The silver finds on those sites have declined over the years, naturally, but I'm hoping that the 800 will find what the other detectors (and primarily me) have missed.
Good luck to all!!!