The trustee has a list of about 20 - 30 simple questions that he or she will ask all debtors. Most of these simple questions will require a "yes" or "no" answer. Some examples are:
1) Is that your signature on the signature page?
2) Is everything in the petition true?
3) Has anything changed since your petition was filed?
4) Do you have a bank account?
5) Do you own a car?
6) Are you expecting an inheritance anytime soon?
Some of the questions will be used to clarify or to double-check what was already indicated in the petition.
Additionally, there may be a few questions specifically addressed to you only. These will be to clear up any questions the trustee has about your petition. An example would be if you did not list clothing as one of your assets (perhaps because the value of your clothing is under $100 [I am not suggesting this is the case - I am just using it as an example that I have heard asked]). Some trustees will ask, "you are wearing cloths, so why didn't you list clothing as one of your assets?"
If you are not the first person called, you will be able to listen to the questions as addressed to other debtors, and if you are not sure of an answer to any of them, you can go outside the room to ask your attorney about that question (if you are using an attorney).
The actual time spent in front of the trustee is usually 15 - 30 minutes. However, the waiting time can be a up to a few hours, depending on how many debtors are on the list ahead of you. (The list will be posted, so that you will know about how long you will have to wait.)
I think this is what you wanted to know. If not, please let me know.