You can do a standard search where you enter the name or business category, followed by the city, state or zip code. What is great about finding white page databases online is that there are many different places to find them, and many of them hold different information.
If you think about all you can find online, you may get overwhelmed, and you may never want to leave the house without your computer. However, when you have the number and not the name, the process is a bit different. This is only if a number is provided to you from the phone owner and it is included in to the reverse database.
It can also be very useful if you want to keep track of a cheating spouse or you want to make sure your kids are safe. You also need to remember that when using reverse yellow pages, you may not be provided with results if the business or person you are looking for is not listed in the public directory, or does not exist within the yellow pages. There are many types of paid reverse phone directories.
Good luck with your investigation. Using the Internet to find out who may be harassing you makes clearing up matters much easier than it used to be.