How do I begin?

Son born 5-26-68 in NewBerlin, WI, adopted in Milwaukee , WI about 4 days later. I was 19 and had mother would wouldn't discuss it ever, then or since. I tried to begin a search twice a while back and it went nowhere. Adoption was done by private attorney hired by adoptee's new parents. They found me thru doctor that made delivery. Hospital and doctor no longer exist. All I know is judge made a scared 19 yr old girl who had just given birth alone swear I'd never try to contact or find son. Faint memory says they named him Gary or Greg...last name sounded like Boehmfeldt, but that could be way off. A week doesn't go by when I don't think about him even after all these years. Mom I used to get calls asking former by maiden name, but she'd hang up..May have been related. How do I get a start...so many sites etc.