I probably going to US around december time. My mum said that I'll will have to undergo an interview in the US embassy. What kind of questions do they ask? Also, why do I have to bring my salary slip, company's trading licenses and certificates?

From your handle I thought you were Japanese? If you're going for a tourist visit you shouldn't need one. (Keep in mind I don't know what they did in the Homeland Security Dept since I've been away.) I thought the US and Japan had a mutual agreement that we could go between countries with a 90 day visa for tourist purposes. At least, I've always been given a landing permit without worrying over visas. (But, I'm American going to Japan. But I swear I thought I saw something stating free movement.)

If you're going for long term business, then I can see them wanting the above information. The gov't fears people will go in without means of supporting themselves and become a burden on society. I believe that's the official explanation, more or less.

If it makes you feel any better, I had to jump though lots of hoops when I came to China and got married. And that's a yearly set of hoops to boot! ;)

As for questions, if it's anything like China, they'll ask your purpose in going, when/if you plan to return to your home country, and stuff like that. Just be yourself, and for goodness sake, if they ask you whether you're planning on returning to your home country, say yes. (Unless you're immigrating to the US, then can't help you.

<font color="cyan">I last went to the US Embassy in London, probably about a year ago now. Maybe a year and a half ago!

They didn't ask me much really. I queued up for about an hour, and the interview lasted five minutes.

I gave them some company details, why I was going, and when I was returning/planning on leaving.

Took five minutes.

Nothing to worry about!

Might alter, depending on what country your from, and what your actually purpose is.</font>

That don't seem too bad. Only 5 minutes. that's short. phew. :D