BEST ADVICE? Smile, people can hear it in your voice. My last three jobs I was hired after a phone interview.
Also, two things to know: you can take a deep breath and THINK before you give your answers. Taking notes on questions helps as well. Also, they will probably be writing down your answers, so there will be dead silent time after you finish. DO NOT feel like you need to keep talking until they do. Give your answer and then stop so they can finish writing and ask the next question...
GOOD LUCK!