One of the ways you can improve your credit is to pay down your credit card balances to one half or less of your approved maximum limit. Anytime you carry balances more than half of your approved credit limit it is considered a derogatory on your credit rating.
Another way to improve your credit rating is to payoff collection accounts and make sure there are no errors in your credit report. If you do find errors on your credit report, resolve them as soon as possible.