There is no benefit to keeping a small balance–and you’re likely being charged at least 18 percent interest. But you should use each of them on a regular basis –or close one of them, probably the one with the highest annual fee — unless you have accumulated points you want to use in the future. Keep your oldest card, for sure, as it demonstrates length of credit history. And when you do use a card, pay in full and promptly. That boosts your credit score.