If you guessed that you can never be an expert before going for an interview, you guessed it right.
In my opinion one can never master interview taking skills. Every interview is unique just because the person taking the interview is ever changing, and even if the same person is taking the interview, he is in a different state of mind each day and each hour of the day.
From my personal experience, the few things that I have in control are to be calm, not nervous, and be gentle in responses, not aggressive. But when an unexpected question comes up, I stumble and fumble, but still keeping calm.
So, always consider your next interview to be equivalent to a new blind date with a girl/boy. You just cannot predict the outcome.
I suggest that you master 4-5 key things that any interviwee should exibit for an interview to be considered good.