Things You'll Need
Instructions
Determine the classification of the player's first rookie card. Not all true rookie cards say "Rookie Card" or "Rookie Season" on them, although the majority do. Many "official" rookie cards are produced by companies that make cards of a player before he gets to his first season as a professional. These types of early-career cards are usually accepted as rookie cards, as they are the first printed cards of a professional player.
Determine if the card is from the player's first professional season. Some card companies produce multiple cards of a player throughout his first season after signing a professional contract. Depending on the league, the grading system used and the buyer market you are dealing with, all or only the first in this series of pro season rookie cards will be considered an individual player's true rookie card. First-season rookie cards usually have only one year of the player's statistics from that first professional season.
Research your potential rookie card. The world of rookie cards in sports memorabilia trading circles is immense and highly organized. Do not be discouraged if the card does not say "Rookie" or if there is another player on the card with the star athlete. Many high-value early cards from players have other teammates included on the card's face.
Research the card's value with a free price guide. Tuff Stuff's Sports Collectors Monthly is a magazine that offers free price guides for many popular sports cards, both in print and in PDF format available through their website. The guides are somewhat limited in comparison to paid membership programs.
Research your cards through paid membership programs. Professional Sports Authenticator, or PSA, and Beckett Media, or BGS, provide detailed price guides with and grading systems with paid membership. These services can tell you how much your card should cost and what to look for in individual rookie cards.
Get your card verified to ensure its rookie authenticity. Sportscard Guaranty, or SGC, PSA and BGS all provide excellent grading systems for your rookie card. Once a card is graded by one or more of these agencies, its price is validated internationally and it can be sold with ease and little worry about bad business and shaky deals.