Find someone with a copy of Fjestad's Blue Book of Guns (2009-10 30th edition) - this is the definitive resource for determining the value of most guns (as far as I know - your mileage may differ). Look on GunsAmerica and other online gun auction sites, go to gun shows, . Be aware that a lot depends on the condition of the gun, whether you still have both cylinders (22 and 22 magnum), how much original finish is still on the gun, how much wear there is on the gun, whether there are any personal identifying marks, whether you have the original box and manual. And most important, once you come up with a number, whether you can actually find an individual who will give you that number. The gun isn't worth anything if no one will buy it.
50-300 usd
150 USD
$150-$200
100-1000 USD or more depending on specifics
$100-250, depending on condition.
Impossible to value on just the serial number. Call Ruger and they will tell you how old.
50-200 USD
Impossible to value with just the serial number.
No way to answer without knowing the caliber.
50-200 or so
125 or so
25-325 usd