Many companies use phone interviews as an initial employment screening technique for a variety of reasons. In many ways, the way you prepare for a phone interview isn't all that different from the way you'd get ready for a face-to-face interview - save for a few slight additions to and modifications of your list of preparation tasks.

Here's what to do:

Treat the phone interview seriously, just as you would a face to face interview.
A phone interview seems so informal on the surface that it can be easy to fall into the trap of "phoning it in" - i.e., not preparing for it as well as you would for an in-person interview. Don't get caught with your guard down. Be sure to research the company, study the job description, and practice your responses to anticipated questions, just as you would for any other interview.

Have your CV and cover letter in front of you.
You'll almost certainly be asked about some of the information that appears on these documents. You might also want to have in front of you any supporting materials that relate to information in your CV and cover letter, like documents you've designed or written, a portfolio of your various projects, or the written position description from your past positions.

Make a cheat sheet.
Jot down a few notes about the most critical points you want to make with your interviewer(s). Are there certain skills and experiences you want to emphasise? Do you have certain interests or passions you want your interviewer(s) to know about and understand? Be sure these pieces of information appear on your crib sheet. Then touch on them during the interview, even if your only chance to do so is at the end of the session when the interviewer asks you if you have any questions or anything to add.

Get a high-quality phone.
It is important to ensure that you can clearly hear all the questions that are asked of you during your telephone interview.  Ensuring you have a working mobile telephone or landline is vital.

Shower, groom and dress up.
Focusing on your appearance, just as you would for a normal interview, will put you in the right frame of mind from a psychological standpoint. You won't do as well in your phone interview if you're lying in bed, for example.

Stand up, or at least sit up straight at a table or desk.
Again, there's a psychological, frame of mind aspect to consider here. But on a more tangible level, research has shown that you project yourself better when you're standing up, and you'll feel more knowledgeable and confident.

Phone interviews can be tricky, especially since you aren't able to read your interviewers' non-verbal cues like facial expressions and body language during the session -- a big difference from the typical interview. But if you prepare well for your phone interview, you won't need to read anyone's non-verbals to gauge your performance. You'll know for sure how you've done because you'll be invited to a face-to-face interview, where you'll have yet another opportunity to prove you're the best person for the job.