This is something I talk about often. Because many if not most people don't know that the weakness interview involves some pretty twisted mind games. The reason this is seldom talked about in the human resource circles is that it is sort of the dark art of interviewing.
What the heck is a weakness interview?! A weakness interview is a tricky setup designed to make you expose a weakness. Professionally speaking it would make sense that you want to find out any weakness in a candidate. But unfortunately it is like a gun. In the wrong hands your dead.
This approach allows you to expose yourself in a personal manner. That's because the questions are controversial situations. For example a interview could ask you to "name a situation where you made a major mistake and how you handled it."
Now on the surface you might be thinking that isn't such a bad example. But BEWARE. this is how they catch you up (take it from a pro). See it isn't the answer but your physical response that they are looking for so your job is to prepare.
The first part of that preparation involves checking your reactions. Don't shift in your chair and always keep eye contact. Also respond quickly. Secondly pay attention to your tone. Make sure it doesn't change. Again the interviewer is trying to get you to a uncomfortable place. Your voice and facial expressions will be the first signs that your there.
The second part involves the HOW in answering the questions. As I tell anyone the best answers to a weakness interview come in the form of short professional responses. Do not let those negative situations they are asking about effect your delivery. A cool calm non emotional yet friendly professional answer may just get you past those rough situational questions.
But I guarantee you that if don't know they are coming or why you could be doomed. So again prepare yourself.