I have a few questions about the TAX on  a used car purchase.
I live in New York State, and I am going to buy a used car.
I know that I will have to pay tax when I go to register the car.
But I would like to know of tax is payed on the book value of the car, or
on the purchase price.  Also, what tax rate is used ?  The owner lives in
Albany (8% tax), and I will be living in Saratoga with 7% tax.  
Do I pay Albany tax or Saratoga tax ?  (the difference is a whole $50)
One more thing, how much does it cost for the usual 2 year registration ?

Did I leave anything out ? What else might I have to know to purchase and
register a used car ?  (I've never done this before.)