If what you're doing now works, keep doing it. Pick a bill and auto-pay it with the credit card, and pay off the card every month.

There is a popular misconception that using your credit card heavily and paying it off every month will increase your credit score faster, but this is not the case. A $4/month Pandora subscription will work just as well. There is another misconception that carrying a small balance on the card month to month is good for your credit, but this is false as well. Pay it off in full every month.