We had interview today and got approved
(marriage based)
Details:
First off, thanks to my excellent planning skill, we only printed our photos 10 min before the interview (there are only 30 of them in total) and put them in a sloppy tiny album. We were 5min late for the interview. Then we had to wait for over an hour
I noticed many people came after us got called in before us, while some people got there earlier but got called after. Anyway, when the interview started, the interviewer mainly went through our file to verify name address etc. Then he asked "how did you meet each other?"; "did u take any trip together?". We volunteered to show our album. Then he asked me my spouse' DOB and birth place. Then "any supporting documents?"
We showed: shared bank account and lease, shared car insurance, supporting letters from our parents
What we didn't have: wedding rings (interviewer didn't notice), shared bills (we forgot all of them). Besides, I thought my case would be somewhat complicated because I overstayed visa F1, had long distance relationship, didn't have a real wedding (only civil ceremony - and there's no friend/family was present at that ceremony), but interviewer didn't ask about those.
Interviewer asked about 10 yes/no questions in the form, then took my I-94 and said I'll receive GC soon. It took only 10min for the interview and was much easier than we thought!!!
My advice to other people: smile a lot and don't act nervous