First start with your known (living) relatives, make a list of who you want to interview. Next, assemble contact information for each name on your list and if possible, confirm that the information is current.
Your next step is to determine who you should contact first. Think about what you really want to know and who might be the most likely to have that information, as well as who would be the most [willing] to share it with you.
Generally, it is good idea to interview your oldest relatives first, as their memories and stories are at the greatest risk of being lost forever and they often know the most about the family. They likely will have some great stories to share, and you will probably find them the easiest to talk to both because they tend to [have] more free time and the majority will appreciate that you are interested in their stories.
When you contact members of your family, let them know you are doing genealogy research and that you want to interview them to learn more about the family history. Ask if they would be willing to be interviewed and what format they would prefer – in person, over-the-phone, a video call, e-mail, etc.
Ask if they would be okay with you sharing the information with others within the family or outside immediate family, such as using the information on a genealogy website or forum.
Individuals who are close to their extended family and/or attend family reunions, may find it easier to contact their relatives, then those who are not. Regardless of the level of closeness you have with the individual it is a good practice to follow good communication etiquette.
Hartley, P. (n.d.). Ready to contact your DNA matches? Here's what to say (and NOT to say). Family History Daily. https://familyhistorydaily.com/genealogy-help-and-how-to/contacting-dna-match/
Wertz, F. (2017, Dec. 18). The genealogy interview: Asking relatives questions to grow your family tree. NYG&B. https://www.newyorkfamilyhistory.org/blog/genealogy-interview-asking-relatives-questions-grow-your-family-tree