In order to sue someone for an unpaid bill, you must know where she resides in order to obtain legitimate service of process for the lawsuit. You can trace a person who owes you money by searching various sources such as phone books, newspaper archives and the county's public records.
Search County Records
Perform a search of county assessor and recorder records, often available on their websites, for counties you know the individual lives or used to live in. Real estate records and personal property records must be updated each year, so as long as the individual is paying his taxes, you should be able to locate him.
Check Criminal Records
Check for traffic tickets, civil lawsuits and criminal charges against the individual you're looking for by searching online court records, such as Missouri's Case.net, to locate a possible address. It's important to have the individual's date of birth, and even a middle initial, to verify that who you're looking for is the same person listed on the cases you find.
Look in the Phone Book
Canvas phone books or, even better, white pages online. Search by the individual's name, a previous address or even a telephone number to see if she remains in the same location.
Dig Through the Archives
Rummage through article archives on newspaper websites in areas you know the individual resided at one time or another. Often you will find helpful information, such as marriage announcements, a listing as a surviving relative in an obituary, or even information about a business he opened.
Hire a Skip Trace Agency
Skip trace agencies use the information you give them to basically check the individual's credit and pull up all known previous addresses and personal property, including the addresses associated with that property. The more information you have about the individual the better, especially date of birth and social security number. Alternatively, use a company specifically designed to locate someone who owes you money, such as US Search. These organizations are much like skip tracers, only they don't require as much information.