Once you have your credit reports, read through them completely. If you have a long credit history, your credit reports might be several pages long. Try not to get overwhelmed by all the information you're reading. It's a lot to digest, especially if you're checking your credit report for the first time. Take your time and review your credit report over several days if you need to.
Credit scoring models usually take into account how much you owe compared to how much credit you have available, called your credit utilization rate or your balance-to-limit ratio. Basically it's the sum of all of your revolving debt (such as your credit card balances) divided by the total credit that is available to you (or the total of all your credit limits).