Just come back from mine, incidentally my third visit to the lovely US Embassy in London.
You will need,
- I20 from the school, signed by the school and you
- A confirmation letter from the school stating the category of a/c you will be using for training
- Visa interview confirmation letter
- SEVIS receipt
- Passport
- 1 passport photo stuck to one of the forms (can't remember which)
- Forms DS-156, DS-157,DS-158
- Evidence of your means of support/paying for course
- Lots of patience (if in London)
- Some newspapers to read (I took three, and it still wasn't enough to keep me going)
All covered in link above though. My experience lasted approx. 3 hours.
5 minutes of talking to the staff at the interview, 2'55" waiting.