Wanting to prepare myself for my trip to the US Embassy for a Visa interview, I searched the net and found next-to-no information on what to do beforehand and what to expect on the day. So I thought I'd give an account of my experience.
I won't go into the process of applying for the visa and booking an interview time in detail, since the information on the official London embassy site and travel.state.gov cover it all adequately. Though there are a few key points I'd like to make to save you getting horrendously frustrated.
When filling out any of the visa online forms, ensure your printer is connected before you start. Many of the forms only give you the one opportunity to print the confirmation page before it's lost forever, and without such pages you won't be granted a visa (For J-1 applicants the confirmation of SEVIS fee payment page has this property).
When completing the DS-160, make sure you save after every page completion, or that data is highly likely to be lost and you'll have to start all over again! The system drops-out frequently, so keep your ds-160 reference code in your copy-paste clipboard so you can sign back in quickly.
When phoning for your visa appointment, phone from a landline, and ensure you have a credit/debit card at hand to pay the MRV fee, and have all other info at your fingertips; the call takes about 10 mins at £1.23/min, but it's the only way!
I arrived at the embassy at Grosvenor Square 30 mins before my allotted appointment time. You get ushered to a queue at the front of the building (a giant golden eagle directly overlooking you from atop the embassy), which leads to an employee stood at a lecturn-style temporary desk to whom you present your ds-160 confirmation page, visa interview confirmation and MRV application fee reciept. The queue then continues to a guard who checks your passport and ds-160.
You then go through a small 'customs-style' security check building where your belongings are x-rayed etc. Electronic equipment is not permitted and you won't be allowed in with any phones/ipods etc. I travelled to London alone, so was left with the challenge of finding somewhere to store my phone before arriving. Since lockers in public places are a thing of the past, I was forced to leave my baggage and phone at the left-luggage store at Euston station which cost £8.50 for 0-24 hours! Apparently coach stations provide cheaper storage, and various shops around London offer to store luggage too, but make sure they're reputable! You are allowed small bags into the embassy: handbags, shoulder bags, small rucksacks etc. along with drinks bottles (you're made to drink some at security), so you don't have to fumble around with loose forms.
Then you follow signs around to the side and into the embassy to a reception desk where you're given a ticket number. To the left is a door leading to a large waiting hall with hundreds of chairs laid out facing a row of TV screens. The visa Courier service desk runs along the back wall, a small vendor of snacks and drinks along the far front wall. To the right is a row of windows numbered 1-11, laid out much like a bank or post office. A corridoor leads to more windows 12-24 and the toilets.
After well over an hour, your ticket number is called out and displayed on the TV, and you make your way to a window (from 1-13). There, you present all supporting documents for your visa application and have your fingerprints scanned. You then take a seat and wait for the same number to be called again. I waited a further 3-4 hours for my number, so I recommend you TAKE A BOOK to keep yourself occupied! Unfortunately, the numbers are not called out in a consecutive order due to different processing times I guess, and so you must be constantly alert! Don't worry if numbers far higher than yours are called; you'll be called eventually! Once called, you make your way to a window (from 14-24) and are interviewed. If your visa is granted, you then make your way to the courier desk where you pay for delivery of your visa ( you must take a credit/debit card with you to do this). Then you leave the same way you came in!
In terms of what questions I was asked as a J-1 applicant, they were not challenging. I was basically asked questions the answers to which were already available on the forms I'd submitted.
The main points they wish to know are:
How you will financially support yourself in the USA.
Whether you genuinely plan to return to the UK.
What factors will ensure your return to the UK (eg. family, finishing studies, a career etc.)
Why you chose America and why you want to study at the particular institution you chose!
That's about all they asked me. It seems the actual interview is very short for most student J1 applicants.
I got the impression that the whole process was just for the US to be sure I existed, and genuinely wanted to persue an education in America for the right reasons.
I hope some of this info helps!
Important Note: This is just an account of my visa experience to help you get a general picture of what to expect. Your visa interview process may vary considerably. The venue, process, permissible items and procedures and prerequisite documentation may have changed since my writing this.