interfacing rfid with at89c51

how to interface rfid with at89c51,
i m not getting any idea i jst know that rfid have a unique id no bt how to store data related to card? lyk if i want to add name and vehicle no to that card then how it colud be acheived? and in case of making apayment through it in any toll plaza how it happen? i mean the collection of money and managing the amount hold by the card ? i m totally new with rfid...if any one have any schematic or any othr file which could help me abt dis pls upload it

No, balance information is usually not stored on the card directly, retailers are gullible not stupid, anyone with the right reader/writer could print unlimited money that way. It's typically an account number(s) that the system looks up internally to find the balance.

hiten09,
You can't store vehicle no. and name in RFID card. You have to store this information in microcontroller.
RFID card have only a unique 16 digit number.
You have to associate name and vehicle number to this card.
Then you have to do all transaction when the valid card is swapped at card reader.

i wanted to purchase a rfid of 125khz , but i dont know its all specifications any any no or company . if any one have any idea pls share and tell which rfid will be easy for interfacing for a beginner