Gregg, most thin womens rings that can have diamonds generally hit in the foil area at the bottom of the screen, far below nickels. If you look where mattockman's rings hit and I think they would hit at 1 or 2 conduct on the digital screen. Some thin rings that have more mass and may hit a little farther up. So the foil range up to the nickel range is a good area to dig and perhaps miss most pulltabs. Of course rings can hit in the the area where pulltabs live too but will require more digging pulltabs to make finds. Beach hunters generally dig from foil probably at least up to zinc. If you have some thin rings around, just scan them and if you use conduct sounds you should notice that the tone is lower than nickel. A simple man's wedding ring usually will hit a little higher than what a nickel is. Most nickels I have dug will hit 5 on the digital screen, I think because they are tarnished, most pulltabs in my area hit at 6 and higher but there are some older smaller rectangle pulltabs that are virtually the same tone and conduct of 5, also there are some smaller older pulltabs with rings that hit where nickels come in. I guess this may not hold true for all areas as there are different manufacturers of pulltabs with different alum alloys so it could be different for other areas.
Mattockman is right too about very small foil hits further over on the left side of the screen and those darn 22 casings hit over there too. Other trash and this one gives me the most trouble as I don't beach hunt is small shredded pieces of alum cans, according to their size, they can hit anywhere from the bottom of the screen on up. Weaker signals or mixed signals can also cause a ring to hit in the area on the left side of the screen.
If you have a goodly collection of pulltabs, a good thing to do is using the Explorer, scan them and mark them with tape and paper with your readings to see how the different styles and sizes sound, that way if you are detecting at a particular site you can ignore the most troublesome pulltab(s). This is about digging using strategy, of course nothing beats digging every non-ferrous signal but most of us are limited by time so sometimes it is necessary to play the odds. It's everyone's own call however what they want to dig and what to ignore.
I have sites around here where there are decades of pulltabs, different styles and sizes which makes it almost impossible to dig them all. Something I do is find specific small areas where rings have a higher likelyhood of being lost, like playground swings and other playground equipment and anywhere where people may be throwing balls and stuff. If I find a clad and it is not very trashy, a lot of times I will dig any lower conductor that is really close by, hoping they lost a jewelry piece also.
Hope this helps.