Did you know that by law you can get one free credit report per year from each of the three credit reporting agencies? It's a good idea to do that and make sure your credit is correct at all times. Here's the link to get your free report without strings attached. Simply select your state and get started.
I would recommend checking one of them every four months. That way you get a regular update on your credit for free and also see what is going on in all three agencies with your report over time. Don't go to freecreditreport.com. They start charging you after three months for the service if you don't cancel it.
I know someone who corrected $48,699 in errors on his credit report in one day.