If you really want to get rid of most of the pulltabs (gold rings too) you can build a pattern, but dont use the select function where you can X out pulltabs as you will lose the nickles then. This goes the same with the screwcaps as you will lose the IH pennies too. I find I use the learn or reject mode or even the edit mode and build a pattern.
One of mine I set up for the trashy area is black out the whole screen, then go to edit and open up the top right hand side with the large cursior halfway accross the screen. Now I will make sure the sensitivity is set low so I dont get any stray signals and go to the learn mode and learn in a nickle with the medium cursior. This will get me the silver, copper and clad plus the nickles and also a few of the pulltabs,but not all of them. Those i do get a signal on i can tell by the digital numbers as a nickle will be 10 ferrous and 6 conductivity most of the time other than a war nickle which can still be the same ferrous, but the conductivity can be 7. Seems to work for me in those very bad areas of pulltabs and sometime i will run iron mask at a -12 or so and when it gets bad just switch the iron mask off and i will be in my program I set up.
Rick