How would one go about finding information about a parent that left him or her as an infant?

[Rebecca]

I would start with my own birth certificate if the parent is listed on it. Order a copy of the long form. There is more information on it than the short one. Use the information on it to order a copy of the deceased parent's birth certificate. You may find you have living grandparents who can give you all the information you need. It's not free, but much simpler than wading through obits, and pretty inexpensive.

If the parent is not listed on the birth certificate, you might try following the job. If the parent worked in a job that is commonly associated with a trade union or professional association, you might get in touch with someone in the area with a long-standing association in that field. They could probably put some feelers out for you, or may personally remember your parent well enough to provide some clues.