Every time you make a transaction with an air miles credit card, you will accumulate a certain number of points based on the amount spent. For example, for every HKD 5 you spend using your card, you could get 15 points which you can exchange for 1 air mile.
Many credit cards also have welcome offers to entice you to sign up for their cards. A sign up reward may come in the form of 20,000 free miles that you'll receive when your card application is approved. For example, Standard Charterd Asia miles MasterCard and BEA Flyer World MasterCard reward customers with Asia Miles upon spending a specified amount with their credit card.
When you accumulate enough miles, you can redeem them the next time you buy flight tickets. If you're lucky enough to receive 20,000 free miles as a welcome bonus, you're already more than halfway towards earning a return flight from Hong Kong to Tokyo.
When you've collected enough reward points on your card, you can exchange these for air miles and redeem them over-the-counter, over the phone, through online banking, or any other method specified by the credit card provider. Banks and airlines have different air mile conversion rates depending on the type of credit card.
When redeeming points, remember that the number of air miles you accumulate doesn't equate to the number of actual miles you will fly if booking airline tickets. For example you might need to collect up to 15,000 air miles in order to be able to redeem a complimentary one-way economy class ticket, as opposed to 100,000 airline miles needed to obtain a one-way business class ticket on the same flight.
You can also use your air miles to upgrade from economy to business class, or business to first class. This can cost around 50,000 air miles or more, depending on the seat class that you want to upgrade to, and the airline offering the flight.
Redeeming points for a companion is also possible at a discounted rate. For example, your business class ticket can cost around 120,000 air miles, but if you buy another business class ticket for a companion, you can exchange it for only 75,000 air miles.
Air miles aren't just for air miles. You can also redeem accumulated points for specific gift items, free entry to events, discounted set menus at select restaurants and other rewards. Such redemptions depend on the air miles reward programme affiliated with that specific credit card.