People-search websites each operate a little differently, but, generally speaking, you can find instructions for opting out of the specific site by locating the Terms of Service.
People-search websites and information databases make money by selling your personal information online. Because they want to keep making money, they’ll make it difficult to remove your personal information. It’s not uncommon for a people-search company to instruct that you send a faxed request or even a copy of your state ID to remove your personal information.
Worse yet, removing your information once doesn’t guarantee that it won’t end up back on that (or another) website in the future. Because these companies get the data from a variety of public and semi-public sources, it’s likely that your name will reappear when they re-index their database.