Consulate Interview Advice

My husband recently got his I-601a approved, we will be on the waitlist for an interview soon, does anyone have any advice on how to prepare for it? What kinds of questions do they ask?

We've been married for 6 years and have 2 kids together. We are home owners, do our taxes together, etc. Its a legitimate marriage but we cannot help but be a little bit nervous/ wanting to overprepare.