Check your local bookstore for Barbie doll pricing guides. The condition of your doll is a major factor on whether or not it is valuable. Owning a doll in excellent-to-mint condition with original clothing (shoes too), and with its orginal box is most desirable to collectors.
This depends on the age, condition, and quality of the barbie doll. The most valuable dolls are those from before 1960, are in mint condition, and have the original clothes. They are worth more if still in the box.
first i would advise you to check the year of publication of the barbie. than search in the internet e. g. ebay for a similar barbie. there you can watch the auction and see, how much it is worth.