Saving money on credit

When the mail arrives I can expect to find at least one application for a new credit card.   For a long time I would just throw them away without reading them.  Then one day I happened to notice that the advertisement said no annual fee and offered me a substantial reduction in my APR if I used their credit card.   I immediately went online to compare credit cards APR and discovered that if I switched two of my cards I could save hundreds of dollars a year in interest payments.  I may have to change credit companies every year but I will go with the ones that offer me the best program.