They not only provide another source for researchers but also provide a recorded image or voice of the past.
Oral history is voluntary .
Your approach should respect the memories and versions of past events as the interviewee presents them. If you are the operator of the equipment and the interviewer you should make an effort to minimize adjustments to the equipment after you have begun the interview. VHS is good, but newer 8mm or digital formats are better. Prepare for your interview by reading published materials as available. If your interview is of a family member, you may want to review genealogy and old photos.