Don't ask too many questions, as this may seem to be rude and be too time consuming for the interviewers. You also don't want to create a negative impression by seeming to interrogate your interviewers. However, if the interview seemed unusually short to you and it did not address any concerns that you may have, then you should be prepared to seize the initiative and ask as many questions as you dare.
If the interviewers seemed somewhat disinterested in you, this may be an indication that they have somebody in mind for the role already. Your asking the right kind of question is your best hope of opening their minds to the possibilities that you represent. Asking the most intelligent and thought-provoking questions may result in a total change in their attitude toward you. If you succeed in changing their mindset, the telltale sign of this will be that they, in turn, will start asking more questions of you and the interview seems to start afresh.
Ideally, you should limit yourself to only asking a maximum of six questions. This should not take up much time nor will it use up any goodwill that the interviewers have towards you. Any more than six questions and you are then running the risk of wasting their time and talking yourself out of a job. On the other extreme, be sure not to ask less than three questions because you will then seem either disinterested or over confident.
The questions in the next section will especially stand you in good stead when it comes time for you to ask your questions. These are seemingly simple questions but it is the answers given to them which will be of great value to you. The answers will provide you with a relatively good source of information as to what it is like to work for this company and the people to whom you will be reporting.
If you find yourself at a loss for intelligent questions, try to remember these and pay particular attention to what is said in response. Also note how they answer your questions. Try to observe the interviewer's body language when they answer each question. The people answering your questions will always try and answer as positively as possible with their words, because that is human nature and they will also try to be professional. You should, therefore, pay more attention to how they say the things that they do, as well as any sudden or dramatic changes in their body language.
Often you will find that the words are positive but their delivery and body language is negative. This is an indication that you asked a question that created some discomfort for them. Such a contradiction is often an indication that what you were asking about may very well be a problem area. Don't be tempted to follow up on this area as you may be creating a too negative effect. Instead make a mental note of this and move on to your next question.
As an aside to the previous paragraph, I'd like to mention that there are people who, when confronted with a difficult or intelligent question, will rather tell you the truth than deal with the discomfort of not being honest with you. This is not to be held against them but instead should be appreciated. You then know you can have a more open and honest relationship with this person in the working environment.