probably they will ask the following:
1. what is your purpose of visit in the US? if you will answer that you are going to visit a relative, be sure you know the complete address and his/her contact number.

2. how long are you planning to stay in the US?
are you planning to work or look for work while in the US?

3. be sure you have your latest bank statement to prove that you can finance your stay in the US especially if your purpose of visit is for tourism.

4. how long have you have been working in Qatar/present company, your position and your duties and responsibilities. (this question they asked from me since i am working with a US company).