The one question you want to ask after a job interview is the one question that you can not ask. The question is of course is "Did I get the job?" No doubt such a blunt question would have made the interviewer uncomfortable and it would probably put you out of the running for the job. Just because you can not ask that the particular end of question, does not mean that you should not ask questions.
In fact, you're encouraged to ask questions. This shows that you have an interest in the position. Questions you should ask our as follows: "When does this position start?" Or "What are the next steps in the selection process?" Do not ask questions about vacation time or mandatory holidays unless you are purposely trying to tank the interview. The questions about the selection process may clue you in on how well the interview went. If they take the time to explain it to you in great detail it shows they may be interested in you. On the other hand, if they tell you that you will hear From them by the letter, it is probably a good idea to look elsewhere.
Just as there are canned questions the interviewer will ask, there are standard questions that the interviewee is expected to ask. You should research the company and write down questions that are unique to position you are applying for. This will show initiative on your part and raise you above the other applicants who have not done this. Let's face it, you can not be too overprepared for an interview.
If you're thinking of leaving one job for another thing you have some latitudes that those who are without work do not. In this case you should inquire about the packages available in this new position. You do not want to leave a good job with good benefits for a job that offers you less. In this situation you need to know things like promotion possibilities, launches, Health Care, and even vacation.