The most important rule in any interview is to be yourself. If you are not what they want you won't get it, and you probably won't want it. If they think you are what they want but you have fooled them, you won't keep it. Imagine loosing a job because you create the wrong impression that isn't you!
First impressions do count, but you don't know what impression they are looking for!
Know something about them; the job; what they are likely to pay; what they can afford to pay; and what you want, but never disclose it untill after they make an offer. If there are no promotion prospects, don't appear to be in search of them.
Untidy cars reveal a lot, tidy cars are a blank sheet of paper; you could have hired it.
One candidate went for a job to find the interviewer sitting behind a large mahogany desk reading a paper. Without looking up the interviewer said: " Bloggs, all you have to do is impress me!"
Bloggs took out his lighter and set fire to the paper!
Bloggs had not checked to see if they had a non-smoking policy!