Full attention!
Believe it or not, a recent candidate for employment, who, by the way, didn't get the job, didn't hesitate to answer his cell phone when it rang during an interview. Leave the phone behind or at least turn it off before you enter the building. Same goes for coffee, food and anything else other than you, your resume, your job application, and your list of references. They don't belong at an interview.
Answering questions
There is nothing much worse than interviewing someone who goes on and on and on... The interviewer really doesn't need to know your whole life story. Keep your answers succinct, to-the-point and focused and don't ramble - simply answer the question.
Enough information
It's really hard to communicate with someone who answers a question with a word or two. I remember a couple of interviews where I felt like I was pulling teeth to get any answers from the candidate. It wasn't pleasant. So, even though you shouldn't talk too much, you do want to be responsive and fully answer the question as best you can.