In reality, some people say that credit cards are the devil, and once you become addicted to them, you will eventually become a "card slave," working for the bank for the rest of your life. In fact, as long as you use the right methods, you can still be the proud owner of your credit card! Today, we'll teach you to be a little clever and take full advantage of your credit card. Using a credit card for free is something younger people are good at...