Once I trained my mind to stop discriminating out nickels and I started to look for the steadier readings (indicates nickels) versus the jumpy nickel-like readings (I use a CTX and Deus) I started to dig a lot more nickels and doubled my Buffalo nickel count. I rarely get out without finding at least 1-2 nickels. I still dig a lot of pull tabs, but I definitely know when I have a nickel by the readings and sounds, and I oftentimes will call nickels correctly before I dig. I actually went back to some heavy hit spots and found nickels that I had discriminated out in my head. Silver is rare, but easy to find. Nickels and gold isn't as common and not easy to get a handle on to make the dig.
If you having problems throw a few nickels on the ground and practice. I actually bought some Buffalo nickels, older Jeffersons and V nickels and started to check the readings and it really helped me find them when I actually went out to detect. V nickels actually read a little lower sometimes on the CTX than Buffalo or Jeffersons, so it matters to practice on all 3.