Hi,I am just back from the interview and finally got the US visa.

The VO is a yong and handsome guy who looks very nice and he was quite patient to the applicants before me,so I didn't feel nervous at all. He started the questions in English directly and the interview only last 1 minute or so. Here are the main questions:
-Have you ever attended **(the travel purchase on the form)before?
-Why?
-You travelled to *?
-Why?
-Do you speak*(another foreign language on the form)?
I wasn't requested to show any additional materials before I was given the green card(visa approved)and the nice greeting of "Have a good trip".

Thanks for the nice VO and this informative forum.Wish you get your visa,too:)

Note:It is necessary to understand the whole process from material submit to interview in advance,otherwise you might be nervous after walking into the consulate and don't know what to do.