I'm always amazed by how often I can tell that a candidate hasn't really prepared for a phone interview. Laziness aside, preparing takes a lot of the stress out of the experience and lets you answer the phone feeling confident and possibly even excited.
Here's what I recommend you do to prepare. Ideally, you'd do this the night before.
1. Go to the employer's Web site. At a minimum, read the "about us" section. Better yet, read enough to get a good feel for their clients, work, and general approach. Don't leave the Web site until you can answer these questions: What does this organization do? What are they all about? What makes them different from their competition?
2. Go through the job description line by line. Think about how your experience and skills fit with each line. Don't be alarmed if you're not a perfect fit; people get hired all the time without being a line-for-line match. The point here is just to get your brain thinking about how you are a match, so that those thoughts are easily retrievable and can be turned into answers in your phone interview.
3. Think about the questions that you're likely to be asked, and write out your answers to each of them. At a minimum, cover these basics: Why are you thinking about leaving your current job? What interests you about this opening? What are your strengths and weaknesses? What experience do you have doing ___? (Fill in each of the major responsibilities of the job.)
4. Think about how you'll answer questions about salary history or expectations, so you're prepared with an answer when it comes up.
5. Come up with two to four questions of your own, because you'll be asked what questions you have at the end of the conversation. Good questions at this stage are clarifying questions about the role itself and open-ended questions about the office culture. You'll also want to ask what their next steps are and their timeline for getting back to you.
That's it. Then, 15 minutes before the call, review your notes from all of the above steps.
If you're not preparing for phone interviews this way, try it next time. I promise you at least a 50% reduction in stress.