What do you do when you have been asked a question that you know you have a good answer to, but cannot think of it immediately? Don't get caught using the typical "I know the answer to that and I will give it to you as soon as I can remember what it is" line that is most often blurted out (either figuratively or, I'm sorry to say, literally by some). Instead, use the Safety Valve Technique. Basically, this technique "allows some steam to escape" while you formulate your answer. If handled well, it will appear almost seamless to even the most experienced interviewer.
Here is how it works. The interviewer has just asked you a question for which you know you have a good answer, but you just cannot think of it at that moment. First of all, repeat back the question with the Parroting Technique. This will buy you a few precious seconds before going on to the next level. If you still cannot put together the answer, you have two "safety valves" left. First, comment on the importance of the question and its context—"I understand the importance of this in regard to…" If you still haven't formulated your answer, turn the question back to the interviewer for comment—"Can you tell me how _____ (subject area) specifically plays a role within your company?"
This technique takes some practice to avoid the "snow job" look, but if you practice it enough (try attending some MENSA meetings to watch the professionals perform), you will find yourself quite ready and able to squeeze precious seconds out of even the most seasoned interviewers.