Become familiar with the information contained in each of your credit reports. They'll all look very similar, even if you've ordered them from different bureaus. Each credit report contains your personal identifying information, detailed history for each of your accounts, any items that have been listed in public record like a bankruptcy, and the inquiries that have been made to your credit report.
However, there is a big myth that you have to borrow money and pay interest to get a good score. That is completely false! So long as you use your credit card (it can even be a small $1 charge) and then pay that statement balance in full, your score will benefit. You do not need to pay interest on a credit card to improve your score. Remember: your goal is to have as much positive information as possible, with very little negative information. That means you should be as focused on adding positive information to your credit report as you are at avoiding negative information.
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.