Becket comes out with a monthly magazine you can subscribe to or buy one issue that lists the values of all cards from the sport. Search by year and manufacture.
Go to your local bookstore, Borders, or Barnes and Noble. You could even go to your local library if you do not want to buy a price guide. Beckett's is most popular, but there are others available.
The best guide by far out there is Beckett's, which deals in four of the major sports, and can give you a listing price of all your rookie basketball cards.
The most common and most reliable source to price any sports cards would be through Beckett. They provide a book and they also have a website to visit.
