Take a deep breath, sit somewhere quiet that doesn't have distractions (i.e. not at your computer and away from pens, paper, and other stuff).
Don't record it, don't take notes, focus yourself entirely on the conversation you're having. If it were an in-person interview, that's how it would be. If you are more visual, close your eyes and imagine a person in front of you and have the conversation with them. Talk with your hand(s), smile, make all the facial expressions you normally would; it will make you sound conversational rather than stiff.
Google interview questions and see what there is. Read up on the company. Nothing crazy, just background. What they do, how they do it. What kind of environment they promote. All that jazz.
Again...deep breath, relax, it's just a person on the other end.