It’s great to ask a relative questions about your family history. Having a list of questions to ask can also make the interview process easier. But it is worth remembering that the details of an event may be remembered over a period of time and not necessarily during a one-hour interview. The interviewee may remember significant pieces of information long after the question and answer session is over.
And no matter how complete or comprehensive the list of questions seems to be, there can always be aspects of a specific family’s history that is not included. There will be questions the interviewee does not think to ask.
One way to ascertain this information is to maintain a relationship with the individual if at all possible–it can be via email, some form of instant messaging, actual telephone calls, handwritten letters, etc. A relative who is a Facebook friend may see your post about something tangentially related to your shared family history only to have it jog their mind about something they had seemingly forgotten forever and you had never even thought to ask about.
Keeping the communication going can help you to locate more information or at the very least allow the interviewee to provide additional details about an event they were only partially able to recollect initially.