When conducting a customer retention interview, the biggest mistake you could make is not preparing enough. This can lead to asking irrelevant or inappropriate questions, missing important insights, and frustrating your customer. To avoid this, it is essential to define the purpose and scope of your interview, researching your customer's profile and behavior, designing a good questionnaire, and setting the right expectations. When defining the purpose and scope of your interview, consider what you want to learn from your customer, how you will use the feedback to improve your product or service, how long it will take, and what format (phone, video, email, etc.) you will use. Researching your customer's profile should include their demographics, preferences, pain points and goals. Additionally, you should research how they use your product or service and how satisfied they are with it. Designing a good questionnaire should involve using open-ended questions that encourage your customer to share their opinions and experiences. Prioritize the most important questions and group them into logical categories. Lastly, set the right expectations with your customer before the interview by explaining the purpose and value of the interview, how long it will take, and how you will use their feedback. Make sure to ask for their consent and availability as well as confirm the date, time and format of the interview. Thank them for their participation and assure them of their confidentiality.