I was determined to land a particular job. Prior to the interview I read everything I could find about the company and I bought, read, and studied this book:
I read every question, took notes, and formulated my answer for every one in the book. Then I studied my answers. When the interview started I had trouble not laughing as virtually every question that I was asked was right out of the book. I got more relaxed as the interview went on because I knew my preparation had paid off in a big way. Yep... I got the job.
A few years later I was on a business trip with the two guys who had interviewed me. They said by the end of the interview that they knew I was going to be the one hired... and I was the second person interviewed - and they interviewed people for three days. Prep pays off.