Have a VERY small balance on each credit card when the statement closes. That means making sure that the 'current balance' is less than 1% (or even less than .1%) of your available credit.
a) Before the due date, pay off even things that are not due yet. b) Best to leave over a few dollars that you spent that month - to be billed on the statement.
If you haven't been doing this already, it will boost your credit score.