Pepper has been doing some interviews lately. I find many interviewees can’t answer one critical question, as clearly as they should: Why should we hire you? As this helpful link from Miriam Salpiter indicates, you need to have some idea about what the company is hiring you for, a bit about the company itself and of course what you bring to the equation.
A job interview, in my view, should be like a play. You set out to leave those in the audience (aka interviewers) wanting more. You must be memorable and you must stand out from the rest of the actors. You have to leave them with some very clear lines that they associate with you and one distinctive characteristic. Most of all, you have to look like you enjoy being on stage and not just showing up because you have a play to do.
One more thing : Look your audience in the eye.