Purchase a money order using the check you wish to cash at your local post office. To find a post office near you, go to usps.com, the United States Postal Office website, click "Locate a Post Office" and type in your area code. Or call 800-275-8777.
If you have purchased the money order in the name of a company or organization, you must have some form of identification proving that you are a representative of that company or organization. Also, if the money order is made out to two people, such as "Tom and Laura," both parties must be present with identification.
Show identification to the teller or employee helping you and sign the money order. Those unable to sign their name should bring a witness when they mark the money order.