This is easier said than done, but reducing the amount that you owe is going to be a far more satisfying achievement than improving your credit score. The first thing you need to do is stop using your credit cards. Use your credit report to make a list of all of your accounts and then go online or check recent statements to determine how much you owe on each account and what interest rate they are charging you. Come up with a payment plan that puts most of your available budget for debt payments towards the highest interest cards first, while maintaining minimum payments on your other accounts.
Next, estimate your monthly spending habits for other expenses such as gas, groceries and entertainment. Create a limit, based on your income, of what you can spend in each of the different categories of expenses. For example, if you tend to spend $400 a month on groceries, try to stick to $300 a month on groceries by making changes like buying generic brands, using coupons, and resisting impulse purchases.