Finding Coins In Circulation?

That kind of depends on how thoroughly you want to be assimilated.

Silver, of course. Pre-1982 cents, as they're worth more than their face value in metal content. There are a large number of Cent varieties, in almost every year; that would require examining each with significant magnification.

Like I said, shallow or deep.

This is really a simple question to reply to. Just save all coins. Don't worry about dates, mint marks, errors, just save them all. Some day in the future when you are old and retired, then dump them all out on a large table and atart searching for STUFF. You will need a few books there in the future about what is worth what. And if that future is far enough away, you may find that the 3009 Lincoln Cents are being issued.

1964 and earlier dimes, quarters and halves, they are 90% silver.

thats pretty much all I hope for in circulation and pocket change