Don't get thrown by a strange question, there's a good answer to every question, you just have to learn to formulate it. There will always be at least one or more trick question in every interview. You have to recognize it for what it is, take your time to answer it and then side step it without appearing to do so. Speak clearly and don't mumble your answers. Nothing can be more annoying for an interviewer than having to lean forward to catch whatever it is that you're trying to say.
Some jobs require a high level of technical competence.
If you are working in such a filed, you should do your homework before the interview and be prepared to explain or demonstrate some technical concept in detail. Never rush headlong into answering a question. The more analytical the question, the more thought process it requires. Remember to think for a moment or two before you begin to answer. Never say you don't know why you opted for a certain topic or course or that someone else picked it up for you.