You are in the middle of an important interview and are confident that you are doing an excellent job of presenting your skills and qualifications for the position. The interviewer asks the next question - and it's a difficult one. You didn't see this question coming and have no idea to answer it. Words catch in your mouth. You start to sweat as your illustrious visions of landing your dream job are rapidly spiraling away at a breakneck speed. What do you do?
For starters, the best offense is a good defense. Preparing for an interview in advance is the best way to ensure that you will be at your peak performance when the time comes to answer the question "Why should you get this job?". Compile a list of interview questions, both general questions and those that are job-specific, that you could potentially be asked. Then practice answering all of the questions. It may be necessary to practice some questions several times until you can clearly present a solid answer. A good rule of thumb is to practice until you are no longer uncomfortable with the question itself or your resulting answer.
Tempting as it may be to dismiss more straightforward questions, such as "Tell me about yourself", you should rehearse your answer to every question. Oftentimes job applicants get so caught up in preparing for the "tough" questions, that they neglect the ones they perceive to be the "easier" ones. As a result, they are ill-prepared to answer basic questions and stumble in their answers.
It would be impossible to think of and practice every question you could be asked, so you will inevitably run across some questions during the interview process that you hadn't thought of previously. When this happens, the first thing to do is take a deep breath. Repeat the question to yourself, either in your head or aloud to the interviewer, to ensure that you have heard the question correctly. Then use your practice sessions to draw correlations between this question and others you have practiced. Is this new question a variation of one you have answered before? Is it similar to any other question? If you can draw a parallel to questions you are already comfortable with, then the new question will not appear so daunting.
Another good tactic is to break the question into smaller components so that you can take it bit by bit. This is especially useful for multi-part questions. For example, imagine you are asked: "Tell me about a time when you found yourself at odds with a team member. What were the circumstances and how did you handle the confrontation". The first thing to do is break this into two parts: (1) provide an example of a team member confrontation, and (2) how did the confrontation get resolved. When answering this question, focus entirely on the first part initially. Set the stage for the conflict that arose, giving the interviewer all of the necessary details. Once this is done, you can then move onto the next part, which is detailing how the conflict was resolved. This is truly the "meat" of the question. The interviewer is more interested in hearing about how you handle conflict and stressful situations than the actual specifics of the conflict itself. So don't skimp on the second part - the resolution. This pattern is true of a majority of multi-part questions: one section of the answer is merely the opportunity to set the stage for the other, more pertinent part(s) of the question.
If you are asked a question you don't know the answer to, it is often better to admit that are unsure of the answer than to try and buffalo your way though an answer. Most interviewers are highly experienced at recognizing "BS" answers and can easily pick up that you making stuff up. If this happens, they will either call you on the table about your fake answer or write you off a being a fraud - neither of these is going to help you land a job. An appropriate response would be to admit that you do not have an answer for the question, but that you would like to do some research at the conclusion of the interview so that you have this knowledge for future reference. Such an answer not only shows integrity, but it also shows that you are not adverse to expanding your learning and are willing to take the extra effort necessary to keep your skills sharp.
A few other helpful hints for answering difficult questions:
It is okay to ask the interviewer to repeat the question if you didn't hear it the first time or if it is a long multi-part question.
It is also okay to ask the interviewer for clarification if the question is unclear.
Never volunteer personal information that is not job-related.
Try to always turn negatives into positives. For example, when asked about your weaknesses, demonstrate how this weakness can also be an asset in other areas.
Relax! Interviewing is a learning process and you will get stronger each time you interview for a potential position. So if an interview goes bad, rather than dwell on it, identify where things went wrong and work on correcting those areas so that you can perform better in your next interview.