When you interview people, start with a list of notes about what you think you know about their relatives and try to confirm as much of that information as possible.
Don't be surprised if people don't remember where their parents were married.
This will allow you to capture their accents, some of their mannerisms and emotions as they respond to your questions.
Tapes have been, for some people, the only record of them speaking after they've passed on.
If you've kept a good record of the book, page number, folio, etc., you do not need a photocopy. Keep a careful record of what searches you have done so far, even if you found nothing.