I've done telephone interviews over the phone before, in my case it was a rather lengthy interview over the phone and done mainly because the job I was applying for was 1800 miles away and they wanted to be sure it was worth flying me there for the final interview. I'm a tech guy so they asked me a fair number of technical questions, so be prepared for whatever questions are typical for your area of expertise.
I know lots of people have said dress up and sit up straight, but I did what was comfortable for me... Jeans and polo. I also tend to wander around when I talk on the phone and I did the same for the interview. *Do* make sure you speak clearly, avoid the "ums", just as you would do in a real face to face interview. Keep your resume handy and any other notes you may need. Keep some paper nearby so you can address questions or make notes about the interview that may be important.
In my case all went well and I was flown out, offered the job and end of story. Good luck with your interview!