Look on the front of the coin to see if there's a small mint mark letter below the date. It may be blank or there may be a D or S.
Numismedia lists the following approximate retail values as of March 2012.
No mint mark (Philadelphia):
Very worn condition - $0.20
Moderately worn - $0.50
Slightly worn - $3.22
Almost no wear - $5.75
Uncirculated - $13.20-$85 depending on condition
"D" mint mark (Denver):
Very worn condition - $0.63 Moderately worn - $1.04
Slightly worn - $5.73
Almost no wear - $33.60
Uncirculated - $62.40-$624 depending on condition
"S" mint mark (San Francisco):
Very worn condition - $0.25
Moderately worn - $1.15
Slightly worn - $5.18
Almost no wear - $16-$19.20
Uncirculated - $51.60-$572 depending on condition
These values are approximate from the best available sources. Values will change over time.