Whether your car was involved in a hit-and-run accident that only allowed you to catch the other driver's license plate number or if you've witnessed a crime, locating a driver by license plate number is a relatively simple task. Make sure you've got the correct number before you begin your search.
Call your local police department. If you've been in an accident from which the offending driver fled the scene, police will be able to locate the driver with a description of the car and the license plate number. Make sure you have the full, accurate license plate number, otherwise it could lead to delays in the search for the other driver.
Check the laws in your state. Most states allow you to file a Request for Record Information at your local DMV. This contains information relating to the registration of a vehicle in the state, as well as any motoring convictions and reportable accidents that are public record. There's usually a form to fill out, and you must sign on the application that you are requesting the information for a "permissible use." Generally, under the federal Driver's Privacy Protection Act, this includes verifying someone's driving record for employment purposes, information required in connection with an accident, or for use in a lawsuit.
You can't just order someone's record because you're curious. In fact, ordering someone's record without having a lawful reason is a crime in some states, punishable by hefty fines in the region of $5,000.
Visit a reverse license plate lookup site like Vehicle Data Registry or Search Quarry. Enter the plate number to search for information on the vehicle's owner. You pay a small fee with your credit card and then search the database for the information. Note that because of the Driver's Privacy Protection Act, the information returned may not include the actual car owner name but be limited to vehicle information and history, VIN data, recall and safety information and possibly some limited owner information.
Hire a private investigator. In situations where you worry that you or your children are being stalked and/or followed, you may want to hire a private investigator to do the work for you. This can be costly: Services start at about $100, depending on the extensive nature of your search.
Using license plate numbers to locate people may be considered a violation of privacy.