1. What is the project on which you will be working in the USA?
2. Whether you will be working at the client site or in your company's USA office? If you said client site, then you may be asked to present the client invitation letter and probably if the client is lesser known name then some photographs of the client and probably its annual revenue etc.
3. Why have you been chosen to go to USA for this project (why not someone else from your company)? Basically i think they want to know how your skills map to the requirements of the project and how confidently can you state them.
4. Your academic qualifications? If you are not a comp. sci. graduate then probably you will be asked to tell where/how you learnt software development skills.
The communication skills matter alot. Some ppl i saw were asked something and they answered something else, and this irritated the VO. Note: The VO has a very short time span to gauge you and so you should give all positive signs about you (especially so by communicating well - ie speak good english). As they say, if you have the right skills then it shows by the way you talk.
My visa interview was brief (lasted 1min or so). The questions asked were the following:
1. Which project was i going to work on in USA?
2. What client?
3. What is my academic qualification?
4. Since i am a non comp. sci grad (a BE in electronics) she then asked me how i learnt software development skills. (any training etc). I said i am working for the past 7yrs in the industry (so most of the skills were acquired on the job plus i had a post graduate diploma from National center for software tech).
Thats all! I hope this post is useful to you. May you have a good experience in your visa interview as i had :).