What is the best possible way to find an adoptee's birth family?

[GrayPict]

It doesn't matter if the site is a subscription one or "free", if you don't use appropriate research methods it is difficult to find information on adoptions or any other information.
You might try looking at the tutorials on Familysearch.org. I believe there is something on researching
adoptions. This is a free site.
I have used free sites as well as subscription sites, and there is some information that is protected by federal law, or court order. Depending on when the adoption took place and where, The records may have been sealed by the court. If that is the case, it takes a court order to have them opened and then they are only available to the adopted person, or the people who adopted. This was generally the case
in adoptions prior to the 1960's or 70's