Even the smallest piece of information may later prove to be an essential clue. Listen to the experience of birthmothers in your group. This is your opportunity to gain some valuable insights into the feelings your own birthmother might have. She probably gave you up because she was told she was doing the right thing. They provide a safe place for you to explore your adoption experience and to gain support from others who are going through their own search processes.
Nice people tend to have smoother reunions.
It is understandable to experience rage at what has happened to you. That rage might even be directed at your birthmother. Deal with the feelings of rage as much as you can before you approach your birthmother. You both will get off on a better foot that way. Only the beginning.