raptor, the main things you will need are the, the name of the card manufacturer, the year of the card, and the players name, and what condition the card is in. just remember that the price you might find is always negotiable, baseball cards are like stocks, they go up and down depending on how many are in population, I would suggest grouping the cheaper cards together and try selling them all at once, then sell your good cards individually. when i was a kid i had millions of baseball cards ( parents threw allot of them away... idiots lol ) and the only way we had to get an idea of how much they were was to go to the store and buy a baseball card "becket(sp)" I'm since the internet revolution they have made them available online by now......
i would just do a search such as.. free baseball card guide, or free baseball card becket, something like that bro. good luck hope you find they are worth allot of $$