Tip:　When you arrive at the Hong Kong airport do NOT buy your Octopus card at one of the vending machines. If you have a foreign passport it is cheaper and easier to purchase it at the special kiosk near the exit to the express train. They could speak English well and will refund your unused card value when you depart. At the kiosk you can also buy a so-called Airport Express Travel Pass, which includes two rides (typically to HK Central and back to the airport) on the Airport express train, AND three days of unlimited travel on the MTR metro, all for around 300 HKD. This combo card is also a regular Octopus card so it can be charged with extra credit as explained above. This is also a way to extend the usage of the card to more than three days.You can add value to the smart card at MTR stations and all retail outlets that accept Octopus payment.

For more pic - http://www.facebook.com/media/set/?set=a.10150320292844163.346956.612199162&type=1