When asking family members questions avoid queries that have "yes" or "no" answers. Open-ended questions such as "why did you leave the county to get married," "where was Grandma born," and "who was Uncle Harry's mother?" are preferable to "did you get married in Mercer County," "was Grandma born in Arkansas" and "Uncle Harry's mother was actually Aunt Sis, right?"
Of course, asking for clarification or confirmation of name or location is sometimes necessary. Just try and avoid questions that suggest answers.
It sometimes is called "leading the witness."
And sometimes you get more detail when you do not suggest the answer.