I never sweat an interview. You have to go into it with the mindset that it is theirs to lose, not yours. You have to believe you have the goods, and even if the job market is crappy it doesn't matter because you have what they need. Even in a bad market houses get sold, cars get sold, and people get hired for jobs that come available. How do you make the sale under those conditions? If you have the right approach, it doesn't matter what the conditions are, you can get what you need everytime if you just go about it confidently. I have turned down far more jobs after the interview than those I have not been called back on. It wasn't always like that, but once I figured out that it was just another sales job, it made a lot more sense. It is not about what you know as much as it is about what you can make the other guy believe.
There was a movie released in 1999 called "Suckers", about the goings on at a used car lot. There is a ring of truth to what is said in that movie about salesmanship, probably the closest thing I've ever heard to the truth. There's a fine line to their approach, and it is easy to become unethical, but if you watch the movie and listen to the monologues from the Sales Manager (the bald headed jerk in the movie), you will hear exactly what I am talking about. It doesn't have to be as cold and ruthless as he makes it out to be, but the underlying truth is universal to successful salesmanship.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)