First thing you should do is look very carefully at some already-graded cards from PSA and Beckett to get a feel for how good a card has to be to get a high grade. Then check Beckett's magazine find out which cards you have are in a good-enough grade to be worth paying the grading fee. I think you'll find you have very, very few cards worth the expense, unless you have cards before 1960 of star players.