what's not to do...is to leave your cell phone on!! Once I had a call which I NEVER expected (and it was really pointless too) during an interview. I refused the call in embarrassment, but that person called again! It was so embarrassing....

also I realized it always help to do research about the company beforehand! One time I had interview with Plush, they asked 'what brands do we carry' and I was like Juicy...uh....and then took random guess XD