How many questions will you be asked in a job interview? Who knows! Hiring managers have very different ideas about how much ground should be covered during an interview and very different estimates of how long it will take to answer a certain number of questions. (Not to mention that different candidates may also take very different lengths of time to respond to any given question.)
However, every question is asked for a reason. We talked previously about why interviewers ask about your weaknesses. You can go even broader than this to talk about the reasons any interview question is asked.
In my experience, almost all interview questions boil down to three main things they want to know about you. And the good news is, if you have solid preparation for these three questions, you'll be prepared for just about anything they throw at you.
1) Why do you want to work here?
Are you just looking for a job, any job? Or do you have a real passion for the work this organization is doing? You help them answer this question through your passion and enthusiasm for the job, your ability to articulate the mission and goals of the organization, and your success in explaining how your past experiences have led you to apply for this job.
2) Are you able to do the job?
At the most basic level, are you competent in the skills needed to complete the work you'd be doing? Often, these are the types of questions asked in an initial phone interview, such as, "Describe your experience using Microsoft Excel." You might also be asked to complete a skills test for some jobs. This allows the hiring manager or search committee to weed out the candidates who don't have the basic competencies. The more specific examples you can provide of your experience doing the work at hand, the better you'll answer this underlying question for them.
3) Why should we hire you over all the other candidates?
Once they've narrowed down the pool to all the people who can do the job, they have to pick the person who's the best fit out of the remaining candidates. The majority of questions you're asked are opportunities for you to provide an answer to this underlying question. Figure out what makes you stand out as a candidate and practice talking about those skills and experiences. Then, no matter what they ask, you can look for an opportunity to plug these key messages into your answer.
Congratulations — you're inside the interviewer's head! By understanding what they really want to know about you, you now have an idea of what you should be preparing and practicing before an interview.