A good way to explore the private investigation field is to get a job or internship in a private investigation agency. Many private investigators have prior experience in law enforcement or the military, so it may be helpful to explore these areas also. Visit the Web sites of professional associations for private investigators, such as the National Association of Legal Investigators, to learn more about what investigators do and the requirements for the work.

Businesses and individuals hire private investigators to gather information about legal, financial, and personal matters. These investigators are licensed to practice in the state in which they work. They may work full time as employees of a private investigation agency or they may be contracted to work on cases for individual clients or organizations such as law firms, and police departments. Their job is to uncover facts and evidence, analyze this information, and report on their findings to their clients. Research work entails interviewing people either by phone or in person, searching public or court records for clues, conducting surveillance, gathering evidence to present in court or to a client, verifying individuals' employment and income, checking for civil judgments and criminal history, and investigating computer crimes and information theft.

The types of cases they are contracted for include investigating possible employee thefts at companies, background checks, proving or disproving infidelity in divorce cases, and helping to locate missing persons.

Private detectives and investigators use a variety of tools. Much of their work is done with a computer, allowing them to obtain information such as telephone numbers, details about social networks, descriptions of online activities, and records of a person’s prior arrests. They make phone calls to verify facts and interview people when conducting a background investigation. When they conduct surveillance, they may sit in a car or in a hidden spot and watch a person's office or home, using binoculars and cameras to observe their activities and collect information for cases. They conduct their work in accordance with federal, state, and local laws, and privacy laws in particular.

Private investigators specialize in different fields. Computer forensics investigators recover, analyze, and present information, such as deleted emails and documents, from computers as evidence in computer crime cases. Legal investigators help lawyers and law firms prepare criminal defenses; they locate witnesses, serve legal documents, and verify facts in civil lawsuits. Corporate investigators are hired by corporations to conduct internal and external investigations; the types of cases they work on might be investigating employee theft or drug use in the workplace, or identifying and preventing fraudulent billing by suppliers. Financial investigators are hired by banks and other financial institutions to investigate individuals and companies that are trying to make large financial transactions. Financial investigators usually are also certified public accountants.