Finding out where a person works is as simple or as complicated as you make it. Personal information, such as place of employment, is generally easy to obtain. Depending on the situation, however, it may require some extra effort.
Ask the person where he works. No night-vision goggles or zip line necessary. Very few people try to hide where they work. If you are uncomfortable asking the question, "Where do you work?" you could ask, "So what are you up to these days?"
Google the person's name. If the person has a common name, try including a state or city name in your search. Many companies will list their employees' names on their websites and searching the Web can help retrieve the information. Additionally, some people have personal websites that include a resume that a Web search will pick up.
If the first two steps fail and you are still doggedly determined, it is time to invest money. A private investigator can easily determine where a person works. Hiring one takes some money, but they'll do all the legwork involved. All you have to do is tell them who you want information on and hand over the cash.
Sign up for a background check website. There are countless websites designed for private investigators and/or employers that want to look into a person's past. These are often pricey to join, but will yield quick and useful results. Search the person's name, and you should get the results you are looking for.