Unless you are a member of law enforcement, you cannot legally find a user's exact location with an IP address; you can, however, use IP lookup services and a WhoIs database to determine the approximate location of an IP address. Tracking the IP to the exact place of business or residence requires a subpoenaed record from the user's Internet service provider.
IP addresses are assigned by the ISP, and standard network traces and other methods do not go past the ISP. However, by using a WhoIs database, it's possible to track down the location of an IP down to the city. Services like iTools, mxToolbox and others provide this information. Access one of these databases and enter the IP address for your query, press Enter and wait for the information to load. Bear in mind that the person could be using a wireless access point or operating from behind a proxy server.
If you need specific information for geolocation, the proper term for finding an IP address, you need to have a valid legal reason such as serious harassment or threats from the person. You then need to report it to law enforcement; if the situation is serious enough, law enforcement can subpoena the records from the user's ISP.