"Linda" wrote
Can anybody give me a
short course in how to tell a good, circulated reproduction of a liberty
quarter from the real deal?

Anything than can be counterfeited will be. I have seen poor copies
of Large Cents and much else, all fairly common. That said, generally
speaking, there is not much reason TODAY to go through the trouble of
making a counterfeit Seated Quarter (or Standing Liberty; you do not
specify which Type). HOWEVER, any uncommon date or mintmark will be
faked.

The usual benchmarks are to look for a "soapy", "bubbly" or rough
surface. Make sure the coin has ridges along the rim (not always a
true test, but one test). Look for casting flash or file marks on the
rim. Basically, the best way to know is to get a genuine coin of that
Type and compare yours to it.