This site helped me a lot. I am paying back by adding my own experience here.
Following questions were asked to me.
1. Hi good morning
2. Do you work for XYZ ?
3. What is your designation?
4. Who's your client?
5. Do you manage the entire IT program for client Organisation?
6. How many employees directly report you?
7. Can you tell me some designations of those who report to you?
8. Can you tell me the month, day and year of your marriage?
Once I answered to this question, asked my wife to confirm the marriage date !
Took about 30 seconds looking through her computer monitor and then said “your visa is approved".
The whole conversation took 3-4 minutes.
No specific questions were asked to my wife.
•In chennai never go too early. You may end up waiting in hot weather. It can frustrate and affect your interview. Going on time really helped me.
•Carry some cash to pay for fluctuation in dollar price. Check this page to calculate the differential amount. http://chennai.usconsulate.gov/consular-fees.html
•Carry photo especially if you have small kids.
•Train and rehearse but don't mug up answers. Confidence is key.
•Get familiar with American accent, just to avoid misunderstanding of questions and giving irrelevant answers.
Good luck !!