Call the operator by pressing "0" on a land phone or "411" on a cell phone. Give the operator the business or person's name, and she will provide all matching listing(s).
Type the person or business's name into an online search engine, such as Yahoo or Google. Often, doing so will lead you to the company website where you can find its contact information; it could also lead you to another website that lists its contact information.
Look it up in a phone book or visit a site, such as YellowPages.com, WhitePages.com or PeopleData.com.