Congrats James! Sounds like you have a veritable goldmine right in the backyard! I'm kind of new to the hobby, So I don't have a whole lot of great advice yet but I have a similiar detector, the White's Prism 3, and I have noticed that the more discrimination you use the less reliable the prism seems to be. Just an observation. Also,Maybe it's just me, but from what I've observed ,my prism doesn't seem to be very accurate at pinpointing. It would probally be wise to invest in a handheld pinpointer.I plan on doing this in the next week or two.
I've noticed that many times I'll dig to the right depth but there will be nothing in the hole, and sometimes I'll find the object after widening the whole a few inches.This is okay when it's in my freinds yard and he doesn't mind me digging large holes (he's usually right by me helping dig,He's a great guy and I think he'll be a convert to the metal detecting cause real soon, he really seems to like the hobby!)But I really don't like digging a lot in public parks.The idea is to be less intrusive as possible.So really ponder investing in a pinpointer or make one out of a cheap stud finder,there are a few pages on the net on how to do this if you are the hands on type of person. As far as where to look, I've had the best luck so far along paths and around benches or picnic tables.These areas are usually littered with trash so be prepared to dig a lot of pull tabs.Around large trees where someone might have spread a table cloth for a picnic to take advantage of the shade is usually a good spot.Think about your own behavior when you go to a park and go to the areas where you would gravitate.Try putting yourselves in the shoes of the people who used to visit the park in the distant past. First hit the high traffic areas, this is where you will uasually have the best luck. Look for any evidence of paths and walkways or sidewalks.Try looking for hills,kids love to play on hillsides and gravity is definetly the metal detectorists best freind when it comes to hillsides, slopes seem to pull change right out of the pockets as if by magic. If you can find any old benches check underneath them, As when people sit , money rolls out of the pockets.Anywhere people sit, this happens, so check what used to be large expanses of lawn that people would have watched a show or picnicked, and around any large rocks or boulders someone might have sat on. Good luck