There are many ways that birth parents and adoptees can locate one another. Below are some options that are commonly used and have lead to successful reunions.
Adopted.com, a Website for birth parents and adopted children to find each other
Try your county Clerk-Recorder. Many states are now passing laws that require them to record requests from birthparents or adopted children, and when both parties request openness, the state/county must connect the two.
Ask a volunteer Adoption Search Angel for help, such as this site or do an internet search for “Adoption Search Angel”
Try a Private Investigator by doing an internet search for “Adoption Private Investigator”