how do I collect money owed on a debt?

First you must sue for breach of contract to obtain a judgment.  After you win the suit and obtain a judgment, there are many different collection procedures open to you, including garnishing wages or other monies being paid to the debtor, or seizing assets of the debtor and having them sold.  These procedures vary somewhat by jurisdiction, and I don't know what they are in Virginia, but, if you don't want to retain an attonrey to represent you (collection attonreys often work on contingency, meaning their fee is a percentage of what they collect for you) the clerk of the court may be able to hellp you.