If you're trying to track someone down and you're able to wrangle a social security or driver's license number, you can use that number to aid in your search. This can come in handy when screening job applicants for potential employment, or trying to determine an insurance premium for a client.

If you have someone's driver's license number on-hand, you can usually access at least part of her driving record, which contains the subject's address. The process varies from state to state, as do laws regarding whether third parties can view driving records. Some states consider driving records public information. Others, like Washington, restrict driving records to the drivers themselves, attorneys, law enforcement and government agencies.

If driving records are public information in your state, check the Department of Motor Vehicles' (DMV) website to see which forms you'd need to fill out in order to obtain a driving record. California, for example, lets you fill out a driver record request application online, while other states might require you to submit requests by mail or in person at the DMV.

In states where driving records aren't public information, you might try finding a record from a state in which the person you're looking for previously lived.

Interestingly enough, the Social Security Administration, which is responsible for social security number, won't provide you with information from a social security number, even if what you're looking for is public record. Your best bet is to instead head to the United States Association of Professional Investigators' (USAPI) website, which contains links to databases where you can research people using their social security numbers.

You might also consider hiring a private investigator, which you can also do through the USAPI website. A private investigator has resources to help you locate an individual starting with just a social security number, though any other information you might have on him (employment, location of previous residences, etc.) would also be helpful.

If the person you're searching for is deceased, or you suspect she might be deceased, you can use her social security number to dig up information using the Social Security Death Index on Ancestry.com. The index contains nearly 100 million records on people whose deaths were reported to the Social Security Administration, and you can use the index to find out where the person of interest died and where she might be buried, if that's the aim of your search.